I have been developing the OPA shield and the last hours are coming for the campaign.
I still need to find bakers that would like to see this project succeed.

The OPA shield brings FM synthesis to Arduino based projects. It can also be used with any computer running Mac, Linux or Windows. I guess you can interface it with Pure Data as the serial protocol is fully documented and the communication library + patch editor are available on git hub.

The current version of the DSP software offers:

• 4-operator voice structure
• 14 different algorithms
• 10 voice polyphony
• 8 simultaneous instruments
• 16-bit high-quality stereo output

It is made for artists, makers and musicians.

If you like the project, please support it:
https://www.kickstarter.com/projects/1304489933/opa-multitimbral-fm-synthesizer-shield-for-arduino?lang=de

Do not hesitate to ask questions here, I am eager to reply.