Wow, very cool! This seems like a great thing to pair with a DX7 and a Reface DX [1], which seems like Yamaha's attempt to take the linage of the DX7 and do it justice in modern form with an increased emphasis on usability. I once had a DX7, and I loved it to pieces.

The DX7 is one of my favorite synthesizers in history, and its software successor, FM8 [2] by Native Instruments is my favorite synthesizer that I regularly use. As with many of the 61-key workhorse keyboards of the 80s, the DX7 is extremely solidly built and has excellent synth key action which makes it a joy to play. It's not weighted, but it also doesn't feel like a toy, and the velocity range (while oddly bound to 0-100, one of its few unnecessary flaws) is very playable throughout the entire range. Beyond that, the DX7 as a synthesizer is technologically a legendary synthesizer that contributed heavily to 80s and 90s music [3][4]. It had great presets, the most recognizable of which is the default patch which is it's rendition of a Rhodes piano. Many folks bought it for that purpose, and you'll that patch in many songs that you may recognize.

The DX7 uses a type of synthesis called FM synthesis, which (sort of like FM radio encoding) allows any of its 6 operator oscillators to be used additively or as an operator which feeds its signal to one or many other oscillators, potentially in a cyclical manner. Operators can use frequency multipliers and dividers with base oscillators (I believe only sine waves for the DX7 although there's a fair amount more in FM8) so that you can have operators sound harmonically many octaves above a base oscillator, or vice versa. In FM8, you can use multipliers anywhere from 0-64 with a 0.001 resolution. Through careful usage of envelopes and oscillator feedback structures, you can go quite a bit beyond your usual virtual analog style subtractive synthesis. but you can do quite a bit of semi-realistic physical modeling and beyond, whether it be orchestral instruments, drums, or punchy cartoonish caricatures of either. It's easily the most versatile form of non-sample based synthesis I've ever found.

The wonderful thing about FM8 is how intuitive and flexible the synth gets once you begin to get used to it. The envelope editor makes it straightforward to create arbitrary stage envelopes with the curvature of each stage customizable and really straightforward to visualize. I personally lean on FM synthesis so heavily for a variety of reasons. It's a taste thing, but it's also a matter of practicality. If you're judicious about patches you use, it's easier to tune FM instruments to make them take up less spectral space, and clash with other elements in a mix without extra post-processing. Additionally that they tend to be quite CPU light, so the number of distinct instances you can run in realtime without maxing out your CPU is a fair amount higher than hefty virtual analog synths like Massive (it may potentially be the same for Spire). Finally, when it comes to soundscape design possibilities, long envelopes and frequency modulation open the door to ambient shape design that is borderline impossible to do otherwise. I believe this is why the DX7 became Brian Eno's favorite synth [4].

FM8 is not free (although it and Komplete were some of the best investments I ever made in my music) but there are a variety of free DX7 synths out there that you can use, some of which are compatible as editors for DX7 SysEx patches. The one I'd recommend is Dexed [5], which is open source and pretty nice, because you can use it with the giant free DX7 patch ecosystem that's built up over decades. Give that a go with REAPER (trialware), LMMS (open source but a little hard to use with VST/AU plugins), Live (evolving and likely the best for professional musicians to create on), or a DAW of your choice and you're in business. Which reminds me, I have a track I need to finish...and based on my commentary, you can probably accurate guess whether there's at least 1 instance of DX7 on it.

[1] https://www.youtube.com/watch?v=O3PGO_DiuYU

[2] https://www.youtube.com/watch?v=lx_L9dPIa78

[3] https://reverbmachine.com/blog/exploring-the-yamaha-dx7

[4] http://bobbyblues.recup.ch/yamaha_dx7/dx7_examples.html

[5] https://asb2m10.github.io/dexed/