I want to begin to dispel a myth which still exists in the guitar community, that is: If you know too much music theory it stifles your creativity when composing or improvising.
Firstly, I think this myth may exist because people don’t fully understand the process which the majority of composers, and improvisors (improvisation is a form of composition) use. Many people seem to think that composers compose with a book of musical rules open in front of them, and are guided by these rules. It’s important to remember that throughout the history of music it was practice which generally preceded theory. In other words, composers composed what they heard in their head and were guided by their inspiration and the theory which they knew. This theory didn’t restrict their compositions; many innovations in music theory came as a result of composers following their inner ears (the development of the Harmonic and Melodic Minor scales for example). Learning theory means internalising theory so that it can be applied to actual music. For example, if a Jazz musician is improvising over a fast tempo tune where there is a change of chord every few beats do you think they are running all of the theoretical possibilities through their head as they play? They don’t have time for this. It is their inner ear which, through the internalisation of music theory, is guiding their inspiration and improvisation.
Even when a composer chooses to base a particular tune on a specific musical device, this device is internalised and it is the ear which guides the composition. For his tune, The Enigmatic, Joe Satriani chose to use the Enigmatic scale as a compositional beginning. I would suggest that Satriani would have catalogued all of the harmonic and melodic possibilities which this scale contains and internalised these sounds, it would have then been his ear which guided the tune’s creation; based on the sounds and theory of the Enigmatic scale.
Music theory can open your mind and ears to different possibilities, but remember, it must be connected to practise for it to have the most benefit.