A few months ago I also got myself a DSP-G1 chip and now I want to build a nice polyphonic synthesizer. The DSP-G1 chip contains everything you need and you could connect it to a MIDI keyboard with a few components and control it with MIDI. But I did not really like that. I want to be able to turn knobs and have some other special functions. One of them is the possibility to save the adjusted sounds. For this I now use an Arduino Nano.
Here are the first photos: