Ardour is a digital audio workstation. You can use it to record, edit and mix multi-track audio. (GPL)
Linux - FreeBSD - macOS
Audacity is free, open source software for recording and editing sounds. (GPL)
Linux - FreeBSD - Windows - macOS
MusE is a MIDI/Audio sequencer with recording and editing capabilities written by Werner Schweer. MusE aims to be a complete multitrack virtual studio for Linux. (GPL)
Linux - FreeBSD
Rosegarden is a professional audio and MIDI sequencer, score editor, and general-purpose music composition and editing environment. (GPL)
Linux - FreeBSD
Zrythm is a cross-platform digital audio workstation designed to be featureful and easy to use. Zrythm offers limitless automation, multi-backend support and is free software. (AGPL)
Cross-platform
5 applications