Browser Editors / Synths

Audioalter, WavaCity, Bosca Ceoil, AudioMass, editor.audio, TwistedWave or xAudioPro - Online Editors

Drumhaus, iO-808, Sequencer64, Drummy, DrumBit, Roland50.studio, Acid Machine 2, orDrumbox or Hydrogen - Virtual Drum Machines

UltraBox, AbyssBox, JummBox / GitHub, BeepBox or GoldBox: Online Sequencer / BeepBox Forks
Efflux: Online Tracker / Sequencer
Sequencer, Draw Audio or DrawBeats: Scale Sequencers
Petaporon or Pianoboi: Piano Sequencers / Instrument Editor
OnlineSequencer: MIDI Editors
WebSynths: Browser Synthesizers
NoiseCraft: Modular Synth Builder
VirtualPiano: Browser Pianos
MK-1: Online Sampling Keyboard
VO Pads: Video Sample Sequencer
React Guitar: Virtual Guitar
Theremin: Virtual Theremin
Pantam Playground: Virtual Pantam
WD-1 or YOU.DJ: Online DJ / Beat Creators
PIXELSYNTH: Image to Sound Synthesizer
Slowed and Reverb: Make Slowed, Reverb and Remixed Songs
BeatMachine or bungee: Audio Tempo Editors
MIDI Recorder: MIDI Keyboard Recorder