
XSSR Academy - Курсы по саунд-дизайну и созданию музыки к играм от аудио-инженеров Wargaming
Learning Synths from Ableton - A very basic online one-hour intro into synths
Helm - A free and open-source easy-to-grasp VST synth with a very friendly interface, a tiny blog on its emergence, a complete manual on 32 pages and a more powerful sequel Vital made by the same engineer


Also, historically there was a number of environments to do sound synthesis with code - starting from CSound, going through an abundance. My understanding is that SuperCollider, Max/MSP and PureData are the most alive now.


Bartosz Ciechanowski. Sound - low-level visualizations of what a sound is
the oxford handbook of timbre
Алексей Насретдинов. Физика и анатомия звука
R-Synth - a random synth generator