Sorry to say but the dsp-G1 synthesizer chip is end of Life as NXP has
ceased production on the NXP LPC-810 8-pin ARM in a 8-pin DIP.
The dsp-G1 is a very popular DIY synth chip introduced 4 years ago.
The remaining stock available here:
and at Adafruit:
will be sold out and no more available.
A sad day for the DIY community indeed!
An Arduino version of the source code for the dsp-G1 will be added later.