Tempo Maps & Song Building#69

Implement the ability to set tempo and metre changes inside of the create a song feature (example: 120bpm 4/4 for 32 bars, 5/4 for 16 bars, 100bpm 5/4 for 16 bars)

This would be incredibly helpful for songs with complex structures or multiple movements.

Additionally, being able to accept metre changes when synced to a DAW would be very helpful.