With a A7 open chord tuning on my cbg, what harmonica can I play....and if it is the key of A haromonica, can I blow in and out? Playing cross harp? I just did a couple of songs and my harmonica was in the key of A.....It sounded pretty good with just one of the strings on my cbg, but I really don't know how I pulled it off more than that. So now, I have swaped out my eye bolt tuners for real tuners,and now I have the strings A, D, G on my cbg, so I am ready to stop breaking too many rules and do things right with tunings since now I have my harmonica thrown in the mix. Why A7 tuning you ask, I can not get my G string to tun to a solid A, so I tuned to the A7 open chord. It sounds good, and I like it, but now I am not sure what harp to play.