I know this is going to sound like a stupid question, but I haven't been able to find the answer anywhere. What is the key relationship for cross-harp playing? In other words, what key harp would you use for playing cross-harp with a blues in A? Apparently all the books I've seen assume you have at least this amount of knowledge, but my wife and I are total neophytes at this instrument.

Thanks in advance.

jeffp