Scaler Music

Scaler Music makes Scaler 3, a music theory plug-in and standalone app that detects keys, scales and chords from MIDI or audio, suggests chord progressions and turns them into melodies, arpeggios and basslines. Scaler 3 replaced Scaler 2, which was sold under the Plugin Boutique name. It runs as VST, VST3, AU and AAX on Windows 8 or higher and macOS 10.14 or higher, natively on Apple silicon.