Tenacity is an easy-to-use, cross-platform multi-track audio editor / recorder for Windows, macOS, Linux and other operating systems and is developed by a group of volunteers as open-source software.

Muine is an innovative music player, featuring a simple, intuitive interface. It is designed to allow users to easily construct a playlist from albums and/or single songs. Its goal is to be simply a music player, not to become a robust music management application. This doesn’t mean Muine has no features! Some feature highlights:
Muine is targeted at the GNOME desktop and uses GTK+ for the interface. Most of the code is written in C#, with some additions/bindings/glue in plain C. Muine was originally written by Jorn Baayen, but now maintained mostly by others.
github.com/mickeyr/Muine
gitlab.gnome.org/Archive/muine
en.wikipedia.org/wiki/Muine
manpages.org/muine
The Daphile is the heart of a digital music system. Its primary focus is in storage and playback of your digital music library. It enables the best possible audio quality and future-proof flexibility by providing plug&play support for USB connected digital-to-analog converters (DAC). You can easily setup a multi-zone system just by connecting another USB DAC for each zone.
Daphile is based on the open source Squeezebox Server, Squeezelite and Linux.
Since Daphile is used and configured completely via the web interface the user is not required to have any Linux skills.

Adds and fixes music metadata and adds album art.
VintageRadio is a GUI front-end for the fm command-line application included with fmtools <http://benpfaff.org/fmtools>. It is written in [incr Tcl/Tk], an object-oriented extension package for Tcl/Tk. VintageRadio is not part of fmtools.

TAL-NoiseMaker is a virtual analog synthesizer with great sound and low CPU usage.

Charlatan is a polyphonic, subtractive virtual analog (VA) synthesizer VSTi plugin with focus on sound quality and easy usability. It comes with a flexible, yet not overwhelming feature set which encourages artists to start tweaking instead of just relying on presets. In spite of it’s simplicity, Charlatan’s architecture is flexible enough to create both classic sounds and rather experimental noises. While making no compromise about sound quality, the sound engine has been highly optimized for efficient CPU usage making Charlatan well suited as a “bread and butter” synth even in projects with a large number of plugin instances. Best of all, it’s freeware! Enjoy!

wrk2mid is a command line utility for translating WRK (Cakewalk) files into MID (standard MIDI files). This project depends on Qt and Drumstick libraries.
foo-RT – A PGGB-RT foobar2000 (Windows) component up samples or down samples your audio tracks in near real-time fashion using insanely long linear filters. We are able to do this by using hardware acceleration PGGB-RT SDK. We say ‘near real-time’ because remastering using insanely long filters require a finite time. Depending on the length of your track and the filter length (in millions of taps) you choose, the very first track will take anywhere from a few seconds to a few ten seconds to start. The subsequent tracks would play in a gap-less fashion
www.remastero.com/foo-pggb-rt-guide
www.foobar2000.org/components/view/foo_pggb_rt
Trivial looking metronome with natural sounds and ‘classical’ approach.

metronomek.sourceforge.io
sourceforge.net/projects/metronomek
github.com/SeeLook/metronomek
flathub.org/en/apps/net.sf.metronomek
This tool forwards audio from an Android 10 device to the computer. It does not require any root access. It works on GNU/Linux, Windows and macOS.
The purpose is to enable audio forwarding while mirroring with scrcpy. However, it can be used independently.