That would be F on a C harp with a 7DB (can't do OBs on a valved harp)? Neat! I'll try it. I have heard of others playing in 12th - I think Carlos del Junco has a couple of tunes he does there.12th is pretty cool, if you can manage the requisite overblow on hole 6--some of the draw bends on the bottom are tough, but it's great for Ionian and Mixolydian.