Yes, it's all software, and FM synthesis is using the same engine as dexed. It's a Blackfin chip, which has pretty good throughput for DSP (digital signal processing). A ton more detail is at [1], including the operating system, which is a FreeRTOS-derived SMP kernel.

[1]: https://github.com/AL-255/FM-1-RE

This thing runs Linux and dexed (an open source dx7 player/emulator) - or any of the myriad vibecoded alt firmwares.