I am trying to improve my ear and the ability to jam along with CDs and other backing tracks. I always seem to come across a small problem when attempting this endeavor.

I start the song and hit and pick several notes on the sixth and fifth strings. I can figure out what key the song is in. Then 60% of the time, (well sort of) I can play along with the song. A lot of times I cannot tell if the song should utilize a minor pentatonic, major pentatonic or a major scale. How does one tell which scale to use over songs?

Example, I pick a favorite instrumental song. I start playing the song in the CD player. I pick notes on the 5th and 6th stings until I find that the song is in the key of “A”. So then I try the A minor pentatonic. It does not sound right. So I try the A major pentatonic. It does not sound right. So now I try the A major scale. It sounds good except on one or two notes. I am now at the point where I am saying to myself that maybe it is an A 7th scale or maybe a diminished scale.

Can any Fretters tell me if I am pursuing this the correct way? If I can figure this out I will be accomplishing a major milestone in my playing. Thanks for any help provided.