Here's the start of a general thread in which to collect resources around the use of the Teensy series microcontroller boards for DIY synthing. For those new to the Teensy, it is a range of arduino-like boards that have gutsier processing capabilities and a few other useful things that make them fun for audio.
You can set them up to use the teensyduino libraries for the arduino environment and there is a version of the Mozzi libraries for making synths.
For 3.xx Teensys, the audio board makes a great addition.
The tutorial video talks you through their audio library and its neat graphic interface to help generate code by patching wires on screen (not realtime like PureData etc., but still handy to save a lot of typing and remembering stuff)
The Teensy 4.0 looks awesome and seems to have a massive speed boost. Do you think the higher power requirements will make it unsuitable for AEM use, or will it still be possible?
At first glance, it would depend on what else you have in your rack, and how many of said racks off the one power brick. I'd let robertlanger make the authoritative pronouncement on this, however, I would imagine, it might simply be a matter of using a 9v adapter with a higher amperage/wattage rating.