Yes you need BOTH. THeory is a great tool to understand music--but in the end, live on stage-with people watching and listening to you--you better be playing MELODIES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! A four note melodie that sticks in your head for 5 hours is much more impressive that a lyidan-augmented scale played at lightning speed against a 7b5 chord in 6/8 time. My point is that music is a language. If you dont connect with your audience then they wont pay to see you again! (and the bar wont hire you back)--------Just think melodies and the BEATLES they wrote the most famouse melodies in the world. if i type YESTERDAY..... you know the melodie thats music!