There's a crazy amount of information to learn about music theory, im studying a BA Music and im still struggling to get my head around it. I reckon it helps if you know at least the basics of music theory. Scales, triads, basic chord progressions. This will give you the basis of your piece you will be creating... This is a good link to learn about Concepts Of Music: http://wrightstuffmusic.com/wp-content/uploads/music-1-aural-concepts-2007.pdf The concepts of music will help you analyse and break down the song, you will have a understanding of how composers/producers intentionally compose their songs.