We had a large discussion about this in the mechanics section a couple months back. It's not the most reliable method, but it works. My understanding is that double-butted spokes should be around A while straight spokes are around G. This is an approximate range, and despite the varying lengths of spokes it still won't vary by more than one whole step in any case. It worked for me in building numerous sets of wheels with 14/15/14, 14ga, and 15ga spokes.

NOTE It did NOT work for me when using revolution (14/17/14) spokes, which would seem to prefer an F but I have not found any experts opinion on this. What it comes down to is that a tensionmeter is the BEST way to check tension, but it's not necessary. I have wheels I have built in 1995 (without a tensionmeter) and have been ridden for many miles without being trued to prove that.

I don't like that key either way. Let's just transpose up a half step and play it in D.