Hello there collective wisdom of talkbass: I'm jamming with a couple of strangers in a few days' time, and one of the songs that has come up is Your Touch by The Black Keys, as linked below The Black Keys - Your Touch - Glastonbury 2010 - YouTube Now, this song only has an electric guitar and drums, so I figured I'll try my best to add in some tasteful, understated lines. The problem now is figuring out the key of the song to anchor my line. I figured that it should be A-something, since the guitarist constantly starts and returns to the A note. Since he plays only riffs and broken chords, how then, does one determine the key of the song? Many thanks in advance for any advice that you can give!