I've never used the word jamming. It's a matter of finding a great song and learning the chords, then slightly altering the vocal melody, and matching a classic chord progression with another chord progression.
M. WardIt was endlessly amusing to me to try to imitate John Lennon and Paul McCartney's harmonies using the guitar.
M. WardTry to take your vision and ego as far away from the song as possible. Give as much respect as you can to the song and the initial inspiration.
M. Ward