Tune your lever harp in E♭ Major. Each string’s tuning with all levers down will be:
C, D, E♭, F, G, A♭, B♭
This is both historically accurate (prior to the invention of the double-action pedal harp), and allows you to play in 14 of the most common keys without re-tuning any strings. The most common key is C Major (the first row in the table below), so think of that as your “home base” lever setup. Though always make sure to lower all levers when you’re done playing!
To use this chart: Match the signature of your music to a signature below. Position the levers (up or down) on your harp as instructed for that key
