# Roland TR-505

The Roland TR-505 rhythm composer is a drum machine and MIDI sequencer released by Roland Corporation in 1986. It hails from the same family of drum machines as the Roland TR-909, TR-808, TR-707, TR-626 and TR-606. The drum kit includes basic rock drum sounds similar to those of the TR-707, plus a complement of Latin-style drum sounds similar to the TR-727.

## Voice synthesis

Samples in the TR-505 are stored as 8-bit unsigned PCM waveforms at a sample rate of 25 kHz. The TR-505 offers some major improvements over the TR-707, including 16 digitally recorded PCM drum sounds (four more than the TR-707) and five Latin percussion voices from the TR-727, reducing the need to buy a separate unit or PCM card.
Summary of drum voices:$^{:9}$
| Low conga | Hi conga | Timbale | Low cowbell | Hi cowbell | Clap | Crash | Ride |
| Kick | Snare | Low tom | Mid tom | Hi tom | Rimshot / sidestick | Closed hi-hat | Open hi-hat |
Although there are 16 drum samples, the TR-505 only has an 8-voice polyphony, restricting some sounds from playing simultaneously: low conga or hi conga; timbale, low tom, mid tom, or hi tom; low cowbell or hi cowbell; hand clap or rim shot; crash cymbal or ride cymbal; closed hi-hat or open hi-hat.$^{:9}$
The TR-505 offers very limited voice editing in the form of volume, velocity, MIDI channel, and MIDI note of each voice as a global parameter.$^{:14,40,42}$

## Sequencer

The TR-505 contains 48 factory sequencer patterns, organized into 3 pattern groups (A, B, and C). The drum machine can also store 48 user created sequencer patterns, organized into 3 pattern groups (D, E, and F).
The TR-505 features five basic modes, including the following:$^{:8}$
* Track play - plays whole tracks (arrangements of patterns to form songs).
* Track write - sequence patterns into tracks.
* Step write - sequence patterns by stepping through each position in the pattern.
* Tap write - sequence patterns by tapping drums sounds in real time.
* Real time - play patterns in real time by tapping the pads.
An accent can be applied to any position in a pattern and will affect all instruments triggered at that position by increasing output volume.$^{:15}$
Users can copy, insert, or delete one or more steps in any given pattern, and copy, insert, or delete patterns anywhere in a track (song).
Each individual pattern is a single measure long, The default time signature is 4/4 consisting of 16 steps and quarter note scale, resulting in each step representing a sixteenth note. Other time signatures can be programmed by changing the Last Step (length of patterns) and the scale, allowing for shuffle and swing rhythms.$^{:24}$
Two or more patterns can be combined, using pattern chaining, to play as a single pattern. Each pattern in the chain occupies a pad, but it will only trigger the chain as a whole, not the individual pattern.$^{:27}$
Up to six tracks (songs) can be programmed using combinations of patterns.$^{:16}$ Each song can consist of up to 423 bars (patterns).$^{:18}$

## Keyboard and external control

The TR-505 consists of 16 individual instrument/ pattern pads. The pads are not velocity sensitive, but can be modified by the accent parameter.$^{:51}$
The TR-505 can transmit and receive on MIDI channels 1 through 16 and Notes numbers 25 to 99. It also contains a MIDI Omni mode allowing it to receive all MIDI data. The TR-505 responds to the following MIDI messages:
* Key message - trigger signal for the individual voice.
* Velocity message - Note-on velocity is both transmitted and received allowing more expressive.$^{:51}$
* Track number message - track/song select
* Bar Number message - Song position
* Clock message - tempo synchronization, start, stop, etc..

## Storage

The TR-505 can store 48 ROM patterns, 48 RAM patterns, 6 tracks, and a maximum of 423 measures.$^{:1}$
The Tape interface (in/out) allow the Tracks and Patterns in internal memory to be stored on external tape. Data can be Saved, Verified, and Loaded from the tape.$^{:35,36,37}$

## Modifications

There are companies, websites, and magazine articles documenting a DIY process for circuit bending and modifying the factory setting of the Roland TR-505. An example of a few modifications include changing audio samples, voice circuit bending, adding individual audio outputs, adding CV outputs, adding pitch change to each voice, and adding circuits to randomize sequences.