Well, this library provides the core functions for classical, Western music theory (scales, keys, intervals, etc.). So any ideas that needs to understand or generate these structures could use them. Some examples off the top of my head:
- Music theory education tools
- Music generation (and the outputs could be transformed to MIDI format for example)
- Piano chord finder
- Music theory education tools - Music generation (and the outputs could be transformed to MIDI format for example) - Piano chord finder
and similar.