<figure><img src="image_1.png" /></figure>

HAL
open science

# Real-Time Collaborative Music Creation on the Web: exploiting Web Audio Modules for Interactive Performance and Composition

Michel Buffa, Tom Burns

<figure><img src="image_2.png" /></figure>

## To cite this version:

Michel Buffa, Tom Burns. Real-Time Collaborative Music Creation on the Web: exploiting Web Audio Modules for Interactive Performance and Composition. 30th IEEE Symposium on Computers and Communications (ISCC), workshop Next-Generation Multimedia Services at the Edge (NGMSE): Leveraging 5G and Beyond, IEEE., Jul 2025, Bologna, Italy. hal-05102625

HAL Id: hal-05102625

https://inria.hal.science/hal-05102625v1

Submitted on 7 Jun 2025

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_3.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Real-Time Collaborative Music Creation on the Web: exploiting Web Audio Modules for Interactive Performance and Composition

Michel Buffa

Université Côte d'Azur,
13S, CNRS, INRIA

Sophia-Antipolis, France

michel.buffa@univ-cotedazur.fr

Tom Burns

tom@burns.ca

sequencer.party

**Abstract**— Advances in web technologies have opened the way to real-time collaborative music applications, enabling musicians to co-create and perform music from anywhere in the world. This paper focuses on the use of Web Audio Modules, an audio plugin standard for the web (WAMs, aka “VSTs for the Web”) in such applications, with a particular emphasis on sequencer.party, a web-based platform for collaborative music creation. We explore how WAMs can form the basis for modular, real-time music composition and performance, enabling users to manipulate audio, MIDI and generative processes in a collaborative way. The presented platform integrates real-time collaborative music installation creation, state synchronization using conflict-free replicated data types (CRDT) and a flexible, track-oriented workflow for live music performance. Through this case study we demonstrate how WAM-based tools can support both educational and performative contexts, offering a new approach to collaborative digital music creation that bridges the gap between traditional environments and web accessibility.

**Keywords**—WebAudio, WebMIDI, Web Audio Plugins, Web standards, Web Audio Modules, CRDT, Collaborative Experience, Real Time Music Performances.

## I. INTRODUCTION AND RELATED WORKS

Real-time collaborative music applications are becoming increasingly widespread, enabling musicians to co-create music regardless of their geographical location [17]. Thanks to advances in web technologies, in particular the Web Audio API and WebAssembly, the browser has become a viable platform for such collaborations.

Web-based collaborative music applications can be broadly classified into four categories:

1. **Real-Time Performance Platforms:** These applications allow multiple users to perform music simultaneously over the internet. Technologies like WebRTC and WebSockets are often employed to facilitate low-latency audio and MIDI data exchange. See this paper for a survey of Network Music Performance Technologies [5].

2. **Collaborative Digital Audio Workstations (DAWs):** Web-based DAWs enable users to work on music projects collaboratively in real-time. Platforms like BandLab or Audiotool use the Web Audio and Web MIDI APIs to provide a seamless collaborative environment. See this paper for a complete review of online DAWs [6].

3. **Educational applications:** Education-oriented web-based music tools, like Multi Web Audio Sequencer [9], Soundcool Online [10], and Audiotool<fnref n="1" />, provide accessible, collaborative platforms for music creation and learning. These tools allow users to work across various platforms without needing large downloads. Multi Web Audio Sequencer is a prototype of an application for segment-based sequencing of Freesound sound clips, with an emphasis on remote collaboration, making it ideal for group learning and experimentation. Soundcool Online is a Web Audio re-implementation of the original Max/MSP implementation of Soundcool, a system for collaborative music and audiovisual creation. It supports remote collaboration, cloud-based sharing, and local sound synthesis, all of which help reduce bandwidth usage. Audiotool, with its modular DAW environment, allows real-time collaboration and project sharing, making it suitable for both individual learning and group music production. In addition to DAW features, Audiotool proposes to add and connect multiple elements such as note generators, instruments, audio effects, collaboratively, for live experimentations. All these platforms are well-suited for classrooms and educational contexts, providing tools that encourage creativity, collaboration, and hands-on learning.

4. **Performance-Oriented Setup Builders:** These tools allow users to construct and configure their performance setups within the browser, either prior to or during the performance. They are often based on modular architectures to ensure flexibility and scalability. Audiotool falls also in this category where we can find some online patchers like WebPD, a WebAssembly port of Pure Data, used also in WebXR applications [11] or JSPatcher [12] (a Max

<footnote n="1">¹ https://manual.audiotool.com/manuals/editor/live_collaboration.html</footnote>
MSP like online application with limited collaborative features).

In the context of web-based applications, "musical performance" can be interpreted in two primary ways:

*   **Audio Streaming Performances:** Here, live audio is transmitted between participants. Challenges include managing latency and ensuring synchronization to maintain the integrity of the performance.

*   **MIDI/State Data Exchanges:** Instead of streaming audio, these applications exchange MIDI data or state information, which is then rendered locally. This approach reduces bandwidth requirements and can mitigate latency issues.

In this paper, we will explore a case study focused on collaborative, web-based live music performances, primarily relying on MIDI/State Data Exchanges (without audio streaming). However, the tool presented, sequencer.party, also belongs to other categories, as it has been used for educational purposes and serves as a "setup builder."

Sequencer.party<fnref n="2" /> has been designed and developed by Tom Burns during the COVID lockdown to enable people to make music together remotely. At its core we find the Web Audio plugin standard called Web Audio Modules (WAM). Sequencer party is highly interactive and can be seen as “a wiki for music” as it allows users to build collaboratively music installations, *during live performances* -there is no need to setup something prior to the performance, although in some scenarios, a preparation step may be planned. In sequencer party, like in Audiotool, people will connect elements in a graph, like in a virtual studio. Available elements, all in the form of WAM plugins, comprise *sound generators* (virtual instruments or samplers that produce audio output), *note generators* (sources of musical notes, either from human input or algorithmic processes like arpeggiators), *real-time effects* (audio processing units that modify sound in real-time, delay, reverbs, etc.) *modulators* (components that influence parameters of other modules, such as LFOs or envelope generators) and audio/video outputs (as some WAM plugins can control 3D objects,ARBGL shaders or manipulate video streams like the one produced by web cams). In native applications, these components are generally implemented in the form of plugins. In the context of this web application, web audio plugin technologies, particularly Web Audio Modules (WAM), play a pivotal role.

In section 2, we present a summary of Web Audio Modules characteristics, with an emphasis on the ones particularly suited for real-time collaborative applications. Section 3 presents sequencer.party main features. Section 4 describes how the collaborative features work (exploiting a well-known algorithm used by multi-users text editors) and section 5 is about how live sessions are handled (invitation links, roles, interaction models). Section 6 describes one of the most original features of sequencer.party: the way it can

handle hybrid performances with remote and face-to-face participation, combining on-stage performance with connected musicians and potentially a connected audience and real hardware instruments in addition to virtual instruments. Section 7 concludes.

## II. WEB AUDIO MODULES: A FOUNDATION FOR REAL-TIME COLLABORATIVE MUSIC APPLICATIONS ON THE WEB

WAM provides a standardized framework for developing high-performance audio plugins that can run seamlessly in the browser, sorts of “VSTs for the Web” [1][2][3][4].

Key features of WAM include *modularity* (facilitates the development of reusable audio components), *interoperability* (ensures plugins can operate across different host applications – they are pure web components), *extensibility* (supports integration with various web technologies, including Web MIDI, WebAssembly,ARBGL, WebGPU, along with a set of extensions for 3D, video, parameter modulation, real-time collaboration etc.), *multimodality* (they can be run without a GUI, or with multiple GUIs, a WAM can be host for other WAMs etc.), and they are *first class web components* (they all have a URI and can be loaded and used like simple web resources -thing about images in HTML).

Hundreds of WAMs have been developed by the community and are available through remote plugin server REST endpoints and can be integrated in host applications using JavaScript dynamic imports or declaratively in HTML, requiring very few lines of code from the host. The WAM ecosystem is alive and evolving [2], and original contributions opens new paradigms for musical collaboration in the browser. Such an example is the recent use of WAMs in collaborative 3D immersive musical applications [7].

Originally proposed to extend the capabilities of the Web Audio API, WAMs provide a standardized interface for real-time audio, MIDI, and control signal processing. As we will see, their architecture makes them particularly well-suited for collaborative applications, especially those requiring synchronous interaction between multiple users over a network.

### 2.1 Multi-Modal Inputs and Outputs

In addition to handling real-time audio streams, WAMs can process MIDI and Open Sound Control (OSC) messages. This flexibility is essential in collaborative settings where musicians and producers may interact with virtual instruments, control surfaces, or algorithmic processes simultaneously. For example, a WAM synthesizer might receive MIDI notes from one participant, audio input from another, and OSC messages from a sequencer or modulation source—all processed in parallel and in real-time.

### 2.2 Parameter Management and State Synchronization

WAMs expose a complete set of parameter controls through standardized getters and setters. These are crucial for implementing automation, UI bindings, and, more importantly, *collaborative control of shared elements*. The API also provides * state* and *setState*() methods, which enable full serialization and deserialization of plugin state. This is a cornerstone feature for

<footnote n="2">² https://sequencer.party/</footnote>
implementing *state-based synchronization* -a model particularly relevant for web applications where event-based synchronization may be inefficient or too bandwidth-intensive.

Unlike event-based systems that require every interaction to be communicated immediately (which may introduce latency or race conditions), state-based synchronization ensures consistency by regularly broadcasting or merging entire states of a plugin or application. This approach is compatible with techniques such as *Conflict-free Replicated Data Types (CRDTs)*, which are widely used in collaborative text editors.

## 2.3 Real-World Implementations

Two notable applications illustrate the potential of WAMs in collaborative contexts are 1) *Sequencer party*: a web-based collaborative sequencer that demonstrates CRDT-based state synchronization in a musical setting. In *sequencer party*, users can collaboratively edit patterns, sequences, and instrument parameters in real time, with conflict resolution and consistency guaranteed by the underlying state model and 2) *WAM Jam Party*: an experimental web-based 3D music installation and live performance tool deployed in immersive, multi-user environments. It enables users to collaboratively place, configure, and perform with WAM plugins within a shared 3D virtual space. In both applications, real-time state updates allow participants to see and hear changes made by others, with consistent behavior across clients.

These examples illustrate that WAMs, when combined with appropriate synchronization strategies, can support both structured musical composition and freeform performance across the web.

# III. CASE STUDY: SEQUENCER.PARTY – A
## COLLABORATIVE WEB-BASED MUSIC SEQUENCER

One of the most advanced demonstrations of the potential of Web Audio Modules in collaborative environments is *sequencer party<fnref n="3" />*. This web-based platform exemplifies the integration of modular audio components, real-time collaboration, and programmable musical behavior—all within the browser.

### 3.1 Plugin Discovery and Modular Architecture

*Sequencer party* dynamically integrates audio components by interfacing with the WAM community endpoint<fnref n="4" />, a centralized service that maintains a registry of available Web Audio Modules. Each WAM plugin exposed by this endpoint is described by a metadata descriptor containing information about its type (e.g., note generator/midi controller, instrument, effect, modulator), its inputs and outputs, and the categories it belongs to. This modular discovery process allows users to seamlessly incorporate a diverse array of plugins into their session, ranging from virtual synthesizers and drum machines to audio effects and modulation sources.

### 3.2 Function Sequencer and Collaborative Programming

A distinctive feature of *sequencer party* is the inclusion of a *Function Sequencer*, which acts as a programmable sequencer engine. Depending on the preset you load (or the script that you write) it can be a MIDI sequencer, MIDI effect, filter, generative music maker and more... Each preset is powered by a small JavaScript program that defines the automation parameters, the UI, and the MIDI events that are generated or modified.

<figure><img src="image_4.png" /><figcaption>Figure 1: WAM programmable Function Sequencer, here loaded with a step sequencer preset (top right).</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 2: Using the "code" button from the Function Sequencer's GUI in Figure 1, the source code of the current preset can be live-coded collaboratively and results seen/heard on the fly by all participants.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 3: Step sequencer with a "Turing machine" preset loaded - a powerful random note generator.</figcaption></figure>

This module enables users to algorithmically define how musical notes are generated, offering complete control over rhythmic and melodic structures. The *Function Sequencer* integrates *Monaco Editor* (Figure 2), the same source code editor component used in Visual Studio Code, enabling *collaborative live coding directly within the browser*. This way, multiple users can co-edit the *Function Sequencer's* logic and graphical interface in real-time, as the plugin

<footnote n="3">³ https://sequencer party/</footnote>

<footnote n="4">⁴ https://www.webaudiomodules.com/docs/community</footnote>
provides a real programming environment for its musical behavior. Several prebuilt presets are provided, including a *Turing Machine* that generates semi-random sequences based on musical keys and scales (Figure 3), a classic *step sequencer* (Figure 1) for creating loop-based patterns a *drum sequencer* with a tailored user interface that visually represents drum kit elements (e.g., kick, snare, hi-hat), a *chord generator* that turns single midi notes into chords. These implementations showcase how procedural and generative approaches to music creation can be collaboratively explored through WAM-based tools. You can see the code that powers each preset by pressing the “Code” button. Edit that code, press “Run”, and your new script is now running. This code window is also multiplayer - invite other programmers and you can edit that file together! Or invite other music-makers and have them play the device while you live-code new features on the fly.

## 3.3 WAM Extensions for Collaboration and Asset Management

The power and flexibility of *sequencer-party* are further enhanced by its use of *WAM extensions*<fnref n="5" />, such as:

* **Collaboration Extension:** Lets plugins manage collaboratively edited text documents, ensuring consistent behavior in shared editing sessions.

* **Asset Extension:** Allows plugins to load or save external assets. With this extension supported, the host environment can handle file operations (e.g., loading/saving presets or user-generated code) on its own server, facilitating for example persistent storage of Function Sequencer presets and other session assets.

These extensions play a key role in making collaborative workflows feasible and robust in a browser-based environment. There are more than ten available WAM extensions, see [2] for details.

## 3.4 Parameter Modulation at Sample-Rate Granularity

Another advanced feature of *sequencer-party* is its support for *sample-accurate modulation*. Certain WAMs are designed to act as modulators, capable of dynamically influencing the parameters of other WAM plugins at the audio sample rate. When a modulation source is connected to a target plugin, the host automatically transmits a list of parameters available for modulation. This enables highly dynamic effects, such as real-time filter sweeps, amplitude modulation, or complex parameter automation, all within a modular, web-based ecosystem. Available parameter modulation WAMs include a step modulator, an envelope modulator, an orbiter modulator and some randomizer modulators. Figure 4 shows a step modulator linked to the Pro-54 WAM synth (a recreation of the Prophet synthesizer). Once connected, the host reveals the synth's parameters (which appear in a drop-down menu within the modulator plugin on the left), allowing for the adjustment of various values over time. These values are interpolated at the sample rate using parameter automation. Multiple parameters can be

modulated (one per line). Figure 5 shows various WAM plugins, such as an orbiter modulator (located at the bottom right). The red circle follows a Lissajous curve whose characteristics can be changed in real-time using sliders, modulating certain synth parameters based on its X and Y positions. The system also supports multiple orbiters and sub-orbiters (the green circles that orbits around the red ones).

<figure><img src="image_7.png" /><figcaption>Figure 4: Sequencer party typical wiring, a step modulator WAM (left) modulating some filter parameters of a WAM synthesizer.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Figure 5: An orbiter modulator (bottom right, modulating some synth parameters (top).</figcaption></figure>

## 3.5 Additional Features

Beyond generative sequencing and modular routing, *sequencer-party* includes a classic MIDI piano roll editor for traditional note editing, a library of dozens of audio effects including filters, delays, reverbs, distortion units, and more—all implemented as WAMs, and flexible routing mechanisms that allow users to connect instruments, effects, and modulators in user-defined configurations.

# IV. ENABLING COLLABORATIVE WEB-BASED MUSIC PERFORMANCE IN SEQUENCER.PARTY

While *sequencer-party* offers a powerful collaborative sequencing environment, it also doubles as a fully modular platform for real-time web-based musical performance. Beyond static sequencing, its infrastructure supports dynamic construction and manipulation of complex signal chains involving note generators, instruments, effects, and

<footnote n="5">⁵ https://github.com/boourns/wam-extensions</footnote>
modulators—all performed collaboratively in real time via a
web browser.

## 4.1 Graph-Based Setup and Track-Oriented Workflow

Within sequencer party, each collaborative session unfolds on a virtual “screen” that conceptually resembles a track in a traditional DAW (Figure 6). A screen occupies the entire surface of the sequencer party window and users can switch between these virtual screens. Each screen contains a graph of components (note generators, instruments, effects, modulators) connected to an audio output. A mixer widget can be used to set the volume of the sound produced by each screen/track (Figure 7) output. Each change on the global tempo, on the mixer and on individual components is replicated in all participant’s session.

<figure><img src="image_9.png" /><figcaption>Figure 6: typical "track/screen" in sequencer party. Track 1 can have a video animated background generated by WAMs that implement the video or the 3D extensions.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Figure 7: on top the mixer component allows to set the volume of each track and create new tracks. Here we see “track 2” of the example from Figure 6.</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Figure 8: A double click on an empty space of a screen displays a dialog for adding new WAM plugins.</figcaption></figure>

On each screen participants can add/delete/move and interconnect a variety of WAM components: note generators, such as sequencers or algorithmic generators, virtual instruments, including synthesizers and samplers, audio effects, from EQs to delays and spatial processors, modulators, capable of controlling other plugins' parameters (Figure 8). These components can be moved and connected/disconnected - they are organized in a graph-based architecture, where participants collaboratively build signal flows. Connections can be made between midi/audio outputs and inputs, or between modulation/control sources and target parameters, providing the flexibility needed for both composition and live improvisation.

## 4.2 Real-Time Synchronization Using CRDTs

To support distributed collaboration, sequencer party uses state-based synchronization backed by Conflict-free Replicated Data Types (CRDTs). This approach ensures that all participants see a consistent view of the session, even when multiple users are modifying elements concurrently.

All structural and behavioral changes in the session—including plugin instantiation and graph rewiring, parameter changes, note generation logic, tempo and transport state, sample assignment in samplers etc. are replicated in real time across all users. The CRDT algorithm guarantees eventual consistency while allowing local responsiveness, which is especially important for maintaining a smooth user experience during live performance.

In sequencer party, all states of the WAM plugins, as well as the state of the graph for each track/screen (connections, positions of WAMs on the screen), and the host's state (tempo, mixer values), etc., are transformed into text documents that are synchronized through a JavaScript implementation of an optimized version of the CRDT algorithm [8]. This implementation is provided by the Yjs library<fnref n="6" /> used by several open-source collaborative text applications. It has also been shown that Yjs is suitable for more general applications that require state synchronization<fnref n="7" /> as it exchanges only the differences when syncing two clients. The library supports various network infrastructures (WebRTC, WebSockets) and even offers support for

<footnote n="6">⁶ https://github.com/yjs/yjs</footnote>

<footnote n="7">⁷ https://blog.kevinjahns.de/are-crdts-suitable-for-shared-editing/ gives more insight about the performance characteristics in Yjs.</footnote>
different types of persistence (e.g., Amazon S3 cloud storage, databases, files, etc.).

### 4.3 Local Beat Synchronization for Electronic Music

Because sequencer party focuses on purely electronic music, the system avoids the need to exchange continuous audio streams. Instead, global tempo and beat information are shared via state synchronization, while beat alignment is performed locally on each client. For instance, if a step sequencer triggers a sampler, the sample (which is already synchronized as an asset) will be played in sync with the local clock, resulting in tightly synchronized playback across all clients without relying on low-latency audio networking. This design ensures that rhythmic structure is preserved, even in the presence of network jitter or delay.

### 4.4 Handling Sample-Rate Modulation

A particularly sophisticated element in sequencer party is its handling of sample-rate modulation. When a modulator WAM is connected to a target parameter (e.g., a synthesizer's filter cutoff), the platform ensures modulation behavior remains both expressive and efficient. This is achieved by synchronizing the state of the modulator (e.g., waveform, depth, rate) and by excluding the modulated parameter from the target plugin's synchronized state. Thus, modulation occurs locally on each client, preserving high-resolution control (at sample rate) without involving the overhead of syncing rapidly changing parameters over the network. This clever separation of concerns allows complex modulation schemes (e.g., LFO-driven vibrato or filter sweeps) to remain accurate and expressive in collaborative sessions.

## V. LIVE COLLABORATIVE PERFORMANCE: ROLES AND INTERACTION MODELS IN SEQUENCER.PARTY

Beyond its capabilities as a collaborative composition tool, sequencer party is mainly used as a live music performance platform. These performances are typically initiated by a primary *organizer*, who assembles a group of collaborators to contribute in real time to a shared, browser-based musical session. This section explores how roles are managed, how real-time interaction works, and how these performances are often streamed and persisted for future use.

### 5.1 Session Initiation and Role-Based Access Control

Live sessions typically begin when the organizer creates a new collaborative session, generating a unique invitation link. This link is shared with collaborators, who can join the session from anywhere using only a web browser. When an invitation is created, the organizer can assign the invited participant a role that will govern his or her level of interaction: a *guest* (read-only) can observe the session in real time, including audio output and UI changes, but cannot interact with any elements, a *performer* (state-level control) can manipulate parameters of WAM components (e.g., synth envelopes, filter cutoffs), but not the signal routing or structure, finally, an *editor* (full control also called “structure control”) can add, delete, or rewire components; change plugins; and edit generative logic or sequence content. He can also create/edit/delete sessions, screen/tracks and assets. This hierarchical control model ensures that the session remains stable and musically coherent, especially during live broadcasts.

### 5.2 Purely Online Performances with Web-Based Components

In its most common form, sequencer party is used for fully virtual performances relying solely on WAM plugins and web technologies. There is no need for external hardware, as all audio generation, processing, and synchronization occur within the browser using the Web Audio API.

Each participant's machine handles its own real-time rendering of audio, while shared session state ensures structural and parametric coherence. We used this setup with students from a master's in music composition to illustrate the concepts of group improvisation and evolving music. While the usage of this platform for education was not the primary goal, the fact that it is accessible, requiring no installations or specialized setup and highly modular, with plug-and-play WAM components, made it a perfect choice for live performance with both remote students and students connected from the classroom. While being an enjoyable experience for making music, it was also useful to introduce concepts of musical synthesis—such as the modular components of an analog synthesizer—and to demonstrate audio effects processing or parameter modulation. The collaborative functionality facilitates classroom interaction, with the organizer's computer connected to a video projector for shared visualization, while students (local and remote), equipped with headphones, manipulate synthesizers and effects in real time. Only the audio from the instructor's machine is broadcast through the loudspeakers of the classroom, ensuring clarity while maintaining individualized exploration.

### 5.3 Real-Time Collaboration and Distributed Creativity

During a performance, contributors can manipulate synthesizer parameters, adjusting tone or modulation in real time, edit step sequences or add/remove drum patterns using the step sequencer or the piano roll editor, use different generative behaviors in the function sequencer, and even participate to simple live coding sessions orchestrated by the teacher/organizer, thanks to integrated Monaco source code editor from the function sequencer, shape effects chains or assign modulators to instrument parameters. All changes propagate across participants via CRDT-based state synchronization, enabling smooth, simultaneous editing without conflicts or latency spikes. CRDT is also capable of handling temporary loss of connectivity as it keeps track of an history of changes, in a similar way Google Docs handles document edition in such cases.

### 5.4 Streaming, Archiving, and Session Continuity

Apart from our experience in classrooms and given the inherently performative nature of sequencer party, sessions from real artists or musicians are usually broadcast live via platforms like Twitch, YouTube, or OBS-based streaming setups. Tom Burns, the author of sequencer party performed multiple times on Twitch. Since the performance takes place entirely in the browser, streamers can easily capture both video and audio directly from their browser tab, providing a frictionless path to online audience engagement.

In addition, sequencer party supports saving and restoring sessions, enabling complex performance setups to be preserved, archived, and resumed at a later time. It also
includes preset and asset management, ensuring the
consistent reuse of samplers, sequences, and plugin
configurations. This persistence allows projects to evolve
over time, making it valuable not only for performances but
also for iterative composition and rehearsal workflows.

## VI. HYBRID PERFORMANCES: BLENDING PHYSICAL INSTRUMENTS WITH WEB-BASED COLLABORATION

While sequencer party excels as a platform for browser-
based music collaboration, it also enables more complex
*hybrid performance setups* that integrate physical instruments
and real-world environments. In this configuration, live
concert elements—such as hardware synthesizers, effect
pedals, mixing consoles, and audience presence—are
combined with the remote, modular capabilities of
sequencer party, creating a multi-layered performance
context.

### 6.1 In-the-Room Setup and Streaming Infrastructure

In a typical hybrid performance, the *main performer* is
physically present in a concert venue or studio, equipped with
hardware instruments, MIDI controllers, and effects units. *A computer running sequencer party* is used as a central
coordination hub and may also serve to interface with
external hardware. A large screen behind the performer
displays the *live session UI*, providing transparency and
context for both in-person and online audiences. An
additional computer running OBS (Open Broadcaster
Software) aggregates audio from the mixing desk, video from
cameras or screen captures, and streams the full performance
on platforms like YouTube Live or Twitch.

This setup bridges traditional live performance
environments with the participatory, distributed world of
browser-based music creation.

### 6.2 MIDI Bridging and Real-Time Hardware Integration

A key enabler of hybrid functionality in sequencer party is
the availability of WAMs that support MIDI I/O. These
modules allow the browser to send *MIDI events* to connected
hardware instruments (e.g., triggering notes on an external
synth), receive *MIDI control messages* from hardware
controllers or pedals, act as translation layers between
software-generated content and physical audio-producing
devices. Moreover, *dedicated WAM controllers* have been
developed for specific synths, including the Korg
MicroKorg (Figure 9), the Roland JX-3P and the Dave Smith
Instruments OB-6.

These WAMs feature *graphical user interfaces modeled
after the original hardware*, including knobs, sliders, and
switches. When used in a session, even remote collaborators
can interact with these UIs to *modify real-time sound
parameters on physical machines*, effectively “reaching
into” the performer’s local setup from anywhere in the
world.

<figure><img src="image_12.png" /><figcaption>Figure 9: *Microkorg WAM patch editor.* As indicated by the invite dialog, the *Microkorg* can then be played over the internet, with *parameters* being adjusted in real time by multiple users.</figcaption></figure>

### 6.3 Multi-Layered Participation: Onsite and Remote

One of the most compelling aspects of hybrid
performances is the diversity of participant roles and
locations: the main performer controls both hardware and
software, acting as the central node in the performance.
Remote participants (musicians, coders, visual artists) can
join the sequencer party session and collaboratively modify
synth parameters, adjust sequences or code behaviors, add or
reroute effects. Onsite attendees may also participate directly
by connecting to the session using laptops, phones, or tablets,
contributing musically or interactively during the
performance.

This layered model of participation introduces a rich
interplay between physical presence, digital collaboration
and real-time creation. It's a new kind of performance,
browser-based yet deeply integrated with the tactile and
expressive possibilities of sound-making.

## VII. CONCLUSION

Sequencer party demonstrates the unique potential of the
browser as a platform for real-time, collaborative music
creation and performance, especially within the domain of
electronic music. At the heart of its architecture lies the Web
Audio Modules (WAM) standard, which provides a modular,
extensible, and high-performance foundation for building
complex audio systems in the web environment.

The integration of WAMs and WAM extensions, such as
those supporting collaborative editing, asset management,
and hardware control—has proven to be a powerful choice.
These technologies allow for a high level of modularity,
interactivity, and user experience that rivals traditional
computer music applications, while remaining entirely web-
native and installation-free.

Coupled with a CRDT-based state synchronization
algorithm, sequencer party achieves persistent and conflict-
free real-time collaboration, supporting a wide range of
scenarios: from remote co-composition and live-coding,
educational use, to hybrid artistic performances involving
hardware synthesizers and audiences.
By integrating state-of-the-art remote synchronization algorithms, advanced browser-based audio processing, modular web audio plugins, and principles from distributed systems design, sequencer-party demonstrates the viability of powerful, real-time collaborative music tools on the web. It offers a level of connectivity, interactivity, and global accessibility that complements—and in some cases exceeds—traditional native applications, all while delivering audio capabilities comparable to desktop software. This exemplifies how the web platform can meaningfully extend and enrich the landscape of music technology.

## VIII. FUTURE WORK

Although sequencer-party has been deployed over several years in a variety of contexts—including educational environments and real-time, geographically distributed live performances—it has consistently demonstrated robustness in terms of system stability and operational reliability. Some deployments have involved more than ten concurrent participants connecting from different countries, using heterogeneous network conditions, and operating over forty Web Audio Modules (WAMs) simultaneously. Despite these promising outcomes, a comprehensive evaluation of the platform is still required. Future work should include structured user-centered studies utilizing validated instruments such as the System Usability Scale [16] to assess usability, the Creativity Support Index [17] to evaluate the system's support for creative processes, the Networked Minds Social Presence Inventory [18] to measure perceived co-presence and collaboration, and the NASA Task Load Index [19] to quantify cognitive workload. In parallel, technical performance evaluations should be conducted to measure critical system metrics such as CPU usage, audio scheduling jitter under high load conditions, and bandwidth utilization during concurrent WAM asset loading. These combined quantitative and qualitative evaluations are essential to rigorously assess the platform's effectiveness and scalability in real-world, networked musical collaboration scenarios.

## ACKNOWLEDGMENT

This work has been supported by the French government, through the France 2030 investment plan managed by the "Agence Nationale de la Recherche", as part of the "UCA DS4H" project, reference ANR-17-EURE-0004

## REFERENCES

[1] M. Buffa, S. Ren, O. Campbell, J. Kleimola, O. Larkin, and T. Burns. 2022. Web Audio Modules 2.0: An Open Web Audio Plugin Standard. In WWW '22: The ACM Web Conference. 2022. ACM, France, pp 364–369. 2022 https://doi.org/10.1145/3487553.3524225.

[2] M. Buffa, S. Ren, T. Burns, A. Vidal-Mazuy & S. Letz. Evolution of the Web Audio Modules Ecosystem. In proceedings of the Web Audio Conference 2024. https://zenodo.org/doi/10.5281/zenodo.10825646.

[3] M. Buffa, J. Lebrun, J. Kleimola, O. Larkin & S. Letz. Towards an open Web Audio plugin standard. In Companion Proceedings of the The Web Conference 2018 (pp. 759-766), 2018.

[4] M. Buffa, J. Lebrun, S. Ren, S. Letz, Y. Orlarey, R. Michon, and D. Fober. Emerging W3C APIs opened up commercial opportunities for computer music applications. In The Web Conference 2020 DevTrack. Taipei, Taiwan. 2020.

[5] C. Rottondi, C. Chafe, C. Allocchio, & A. Sarti, An overview on networked music performance technologies. IEEE Access, 4, 8823-8843. 2016.

[6] M. Buffa and A. Vidal-Mazuy. "WAM-studio, a Digital Audio Workstation (DAW) for the Web." Companion Proceedings of the ACM Web Conference 2023. 2023.

[7] M. Buffa, D. Girard, & A. Hofr, Using Web Audio Modules for Immersive Audio Collaboration in the Musical Metaverse. In proceedings of the IEEE 5th International Symposium on the Internet of Sounds (IS2) (pp. 1-10). Erlangen, Germany. 2024.

[8] P. Nicolaescu, K. Jahns, M. Derntl, & R. Klamma. Near real-time peer-to-peer shared editing on extensible data types. In Proceedings of the 2016 ACM International Conference on Supporting Group Work (pp. 39-49). 2016.

[9] X. Favory, X. Serra, Multi Web Audio Sequencer: Collaborative Music Making. Proceedings of the Web Audio Conference, Berlin, Germany. 2018.

[10] R. B. Dannenberg, H. Zhang, A.K Meena, A. Joshi, A. Kuran, & J. Sastre. Collaborative Music Creation and Performance with Soundcool Online. In Proceedings of the Web Audio Conference (WAC), Barcelona, Spain (pp. 5-7). 2021.

[11] D. Dziwis. PdXR-the Evolution of Pure Data into the Metaverse. In Proceeding of the International Computer Music Conference (ICMC) (pp. 1-8). 2023.

[12] S. Ren, L. Pottier, and M. Buffa. "Build webaudio and javascript web applications using jspatcher: A web-based visual programming editor." In Web Audio Conference 2021.

[13] D. Dziwis, H. Von Coler and C. Pörschmann, Orchestra: a toolbox for live music performances in a web-based metaverse. *Journal of the Audio Engineering Society*, 71(11), pp.802-812. 2023.

[14] D. Dziwis, H. Von Coler and C. Porschmann, October. Live Coding in the Metaverse. In *2023 4th International Symposium on the Internet of Sounds* (pp. 1-8). 2023.

[15] L. Turchet, and S.Krstulović. "DSP as a Service: Foundations and Directions." IEEE Open Journal of the Communications Society (2024).

[16] J. R. Lewis, "The system usability scale: past, present, and future," *International Journal of Human-Computer Interaction*, vol. 34, no. 7, pp. 577-590, 2018.

[17] E. Cherry and C. Latulipe, "Quantifying the creativity support of digital tools through the creativity support index," *ACM Transactions on Computer-Human Interaction (TOCHI)*, vol.21, no.4, pp.1-25, 2014.

[18] F. Biocca and C. Harms, "Networked minds social presence inventory: (scales only, version 1.2)." *Measures of co-presence, social presence, subjective symmetry, and intersubjective symmetry*," 2003.

[19] Hart, Sandra G. "NASA-task load index (NASA-TLX); 20 years later." *Proceedings of the human factors and ergonomics society annual meeting*. Vol. 50. No. 9. Sage CA: Los Angeles, CA: Sage publications, 2006.