Project image

iOS app that writes chord progressions

About the project:

Did you know that music is more like code than most people realize? Notes and chords can be abstracted into numbers and relationships, just like code.

Given my musical background, I wanted an iOS application that could write chord progressions for me and help me tranpose music easily. Given a starting key, Chordpanion generates a set of commonly used progressions in such a key, and provides formulaic progressions to change to another key.

Chorpanion is not currently published to the App Store, but I hope to finish and publish it at some point in the future!

Technology used:

iOS, Swift

View on GitHub


Chordpanion is a work-in-progress iOS app that can write chord changes.

Chordpanion demo

General Premise

Music can be broken into scales and chords, which can then be further divided into notes. There are only 12 unique notes that can be played (although they can be replicated in other octaves). If we assign a number 0 through 11 to each of these notes, we can process them with programming. Chordpanion uses commonly known chord progressions and trasposition techniques to build progressions for a given key.


One of the most common progressions is I vi IV V. This progression can be replicated in any key. However, we can also make observations between the relationships between each chord in this progression. The I and iv chords are built off the same scale, meaning that any transition from I to iv or from iv to I will sound powerful. Similar conclusions about other chord relationships, such as knowledge of the Circle of Fifths, allows Chordpanion to build cool progressions.