SynthEngine

SynthEngine is a powerful GML-only multi-osc synthesizer for GameMaker. It supports all of the traditional controls and settings that you'd find on a synthesizer plugin you might find in your digital audio workstation. It includes a playable demo, has extensive documentation, and is totally free. 

If you want more waveforms, features, and synth presets, check out SynthEnginePro!

	SynthEngine	SynthEnginePro
Multi-oscillator	✔️	✔️
Custom waveforms	✔️	✔️
Waveform presets	4	20
Per-oscillator amp and tuning	✔️	✔️
ADSR Amp Envelope	✔️	✔️
Global panning	✔️	✔️
Render to buffer/audio	✔️	✔️
Multi-LFO	✔️	✔️
LFO connections to panning	✔️	✔️
LFO connections to amp	✔️	✔️
LFO connections to pitch	❌	✔️
Noise generators	❌	✔️
GML processor generators	❌	✔️
Presets	0	20
Price	FREE	$7