For precision low frequency work.  Cutoff frequency between 1Hz and 150 Hz with variable fractional rolloffs between 1dB/oct and 24dB/oct.

https://091audio.de/#hpdoctor

Uses their ‘True Circuit Simulation” technology. $89 normal  price.

https://schulz.audio/products/schulz-tonebreaker/

Capture the sound of low budget home keyboards. Normal price $99.

https://audioplugin.deals/product/cheap-keys-by-sonic-nomad/

https://lp.soundparticles.com/may-melody-sale-2026

Until May 26

From Krotos website: Sound Design Bundle 3 is a powerhouse of sound design, capable of delivering complex sound effects that will leave your audience in awe.

https://www.krotosaudio.com/p/sound-design-bundle-3/