The circle of fifths is a well-known music theory tool that (among other things) gives you a visual guide to the relationships between keys and chords. As such, it can prove useful during your songwriting sessions.
Now ToneGym has introduced an interactive version of the circle that enables you to change the tonic, mode and layout to make it even more accessible.
The circle of fifths is useful because, rather than displaying keys in chromatic order, it puts closely related ones next to each other. They’re ordered according to the number of sharps and flats they contain - go clockwise and each consecutive key gains one sharp; go anti-clockwise and each consecutive key gains one flat - which enables you to quickly identify harmonic relationships.
In ToneGym’s circle, clicking on a note name plays its triad chord, while Alt-clicking plays its seventh chord. If you hold Ctrl/Cmd while clicking the note you click becomes the tonic and related keys are highlighted.
You can access the circle of fifths now on the ToneGym website.