Didn't want to hijack the other thread to post this.. Here's one that I found a long time ago that can be fun and very easy to use.. I taught this to my son-in-law who did not play guitar, but had a sharp ear and loved blues..He caught on so quickly that I had to turn his volume down.. It's an A9th.. Play it open, (for A) 5th fret, (for D) 7th fret (E) for 3 chord blues or jazz All ya gotta do is drop the 4th string 1/2 tone to C#, Then open strum is an A9th.. I've used this for slide as well. Try it..Play a 3 chord blues in the key of A.. Have fun..