Oxid is a free software instrument for Microsoft Windows (VST2/VST3/CLAP) and Apple macOS (VST2/VST3/CLAP/AU) simulating the classic ARP Omni-2 Polyphonic Synthesizer from the 1970s...
Released in 2001 and maintained for 20 years, Frohmage Filter has from the beginning been an insanely popular filter with millions of cumulated downloads.
This virtual instrument has been designed with modern pop & rock production in mind, but it suits well to any music style. And the best thing is, that the MonasteryGrand is free.
The Full Bucket Vocoder FBVC is a software plug-in for Microsoft Windows (VST2/VST3/CLAP) and Apple macOS (VST2/VST3/AU/CLAP) simulating the classic KORG VC-10 Vocoder from 1978.