Continuing the discussion from What do you use to make sounds?:
Chow Kick - Drum Synth for iOS, Linux, MacOS, Windows
Chow Kick is based on ‘creative physical modelling of old drum machine circuits’. Along with a highly parameterizable pulse shaper, Chow Kick uses a resonant filter with several nonlinear modes, creating a wide range of possibilities for sound designers. The kick drum can also be easily “tuned” with incoming MIDI notes to match the key of your song
OctaSine - VST2 FM Synth for Linux, MacOS, Windows. FOSS
Developer Joakim Frostegård has introduced OctaSine, a free and open source FM VST2 synthesizer plugin that the developer say “draws inspiration from the Elektron Monomachine, as well as from NI’s FM8”.
Works on macOS, Windows and Linux Four operators with independent parameters such as volume, panning, modulation index, feedback, three different frequency modifiers (ratio, free and fine) and ADSR volume envelope parameters. The operators can be independently switched to white noise mode Flexible routing allowing setting the output operator (with some limitations) as well as the percentage of signal that is simply added to the final output, enabling additive synthesis. By default, operator 4 is routed to operator 3, operator 3 to operator 2 and operator 2 to operator 1. Modulation panning (!), not present in FM8 Master volume and master frequency parameters Four LFOs capable of targeting most operator parameters as well as most parameters of lower index LFOs. 128 voices Fully automatable Preset handling SIMD-accelerated audio synthesis with runtime feature detection for less CPU usage
Ossia Score - FOSS audio visual sequencer. Midi, OSC, Video, VST support.