Wondering if anybody has tried these synth techniques with the audio adapter or just the Teensy alone.

From this article:
"Wendy Carlos used a system on her 1986 album Beauty in the Beast, where one electronic keyboard was used to play the notes, and another used to instantly set the root note to which all intervals were tuned, which allowed for modulation." Basically, the tuning changes slightly depending on what chord is played. Without this tuning adjustment, some chords will have beats, even if all the notes are in the same key, and even with just intonation. This is especially noticeable with minor chords or square waves. It would be really interesting to hear this feature for playing MIDI files.

And these synth techniques:
Seems like looping quasi-periodic tables with a random starting point whenever a note is played would work to reduce processor load. Maybe high-resolution tables could be used for multiple frequencies by interpolating values. Maybe the Teensy 3.6 could do the floating-point math outright without tables. With mixing the harmonics and enveloping it might sound really nice.

These methods might seem contradictory to each other. The first is about exact mathematical relationships, while the second is about inexactness. Maybe they wouldn't sound "good" together, or maybe they would. Much is subjective.