Editing Trainer and Encounter music for battles (BW1)

[CalWhimsical]

I don't know if this is a topic discussed in the past (it probably has) and I have a general idea as to where I need to edit to get this, but I know very little about the hex data of the games. I want to edit particular Trainer classes' encounter and battle themes. How can I edit what songs play? I can provide a list of which Trainers and which songs I want to use if need-be.