awesome-audio

• Guitarix
• LinuxAudio
• LinuxAudio Members
• lmms - Cross-platform music production software.
• Music Made With Linux
• Qtractor - Qtractor is an Audio/MIDI multi-track sequencer application written in C++ with the Qt framework.
• radium - A graphical music editor. A next generation tracker.
• yabridge - A modern and transparent way to use Windows VST2 and VST3 plugins on Linux.
• zrythm - A highly automated and intuitive digital audio workstation.

DIY guides

• PiFX - A Raspberry Pi-Based Pedal Board.

RaspberryPI

• mt32-pi - 🎹🎶 A baremetal kernel that turns your Raspberry Pi 3 or later into a Roland MT-32 emulator based on Circle and Munt.

MIDI

• Web MIDI - MIDI Support in Web Browsers
• webmidi - WebMidi.js helps you tame the Web MIDI API. Send and receive MIDI messages with ease. Control instruments with user-friendly functions (playNote, sendPitchBend, etc.). React to MIDI input with simple event listeners (noteon, pitchbend, controlchange, etc.).

Synth

• fluidsynth - Software synthesizer based on the SoundFont 2 specifications.
• Qsynth - Qsynth is a fluidsynth GUI front-end application.
• Surge - Synthesizer plug-in (previously released as Vember Audio Surge).
• Zynthian - the Open Synth Platform, based in Raspberry Pi and Free Software.

Effects

• pedalboard - A Python library for adding effects to audio.

More resources

• awesome-python-scientific-audio - Curated list of python software and packages related to scientific research in audio.
• rncbc projects - Project list by the Qtractor developer.

Web - JS Audio

• AudioMass - Free full-featured web-based audio & waveform editing tool.
• web audio api - web audio api is the most basic building block for audio on the web.
• howler-js - howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio. This makes working with audio in JavaScript easy and reliable across all platforms.
• tone-js - Tone.js is a Web Audio framework for creating interactive music in the browser. The architecture of Tone.js aims to be familiar to both musicians and audio programmers creating web-based audio applications. On the high-level, Tone offers common DAW (digital audio workstation) features like a global transport for synchronizing and scheduling events as well as prebuilt synths and effects. Additionally, Tone provides high-performance building blocks to create your own synthesizers, effects, and complex control signals.
• amplitude-js - AmplitudeJS is a lightweight JavaScript library that allows you to control the design of your media controls in your webpage -- not the browser. No dependencies (jQuery not required). AmplitudeJS is available under the MIT License.
• peak.js - Peaks.js was developed by BBC R&D to allow users to make accurate clippings of audio content in the browser, using a backend API that serves the waveform data.
• Tuna - An audio effects library for the Web Audio API.