Reaper

Reaper is a cross-platform app from Cockos Inc. for multi-track audio and MIDI recording, editing, processing, mixing, and mastering. Features include multi-source recording, non-destructive editing of audio “in almost any imaginable way”, track layering, hundreds of audio and MIDI effects, support for all kinds of hardware and plug-ins, track metering, automation, pitch shifting, a project management “bay”, customizable user interface, and “the highly flexible ReaSurround plug-in – apply rotations, transformations, and diffusions, and even automate the positions of the speakers themselves.” (See Reaper user guide [PDF], Quick Start [PDF] and other resources for more details.)

Reaper 6.0.2 is priced at $60 for personal use ($225 for commercial use) and downloads support Mac OS X 10.5 (!) through macOS 10.15, as well as Windows and Linux (“experimental builds”) and the WINE environment. The download is “a free, fully functional 60-day evaluation. No registration or personal details are required.”