midi.city has been created with the help of hundreds of different open-source projects and with contributions from many others.

• Tone.js by Yotam Mann: the Web Audio API-based sound engine that implements a majority of nodes used in the audio graph. It powers many of the advanced features used such as Granular Synthesis, Reverb, and timing.
• Groove Monkee: graciously provided the MIDI files that are used for the percussion loops.
• Keenan Brand: created the midi.city logo and various icons used on the site.
• Noun Project: various icons are used via a Pro license.
• Google Material Design: various icons.
• Compifont by Marcin Dziembor: the soundfont powering the samples and many the audio graph definitions, is originally . Several modifications have been made to adapt to midi.city and the Web Audio API.