I've found a suitable solution for anyone curious/noobish (like myself):
1) Take "ChargedFire.asm" and change the extension from ".asm" to ".txt".
2) Open it up and take a looks at these lines:
!SFX1 = #$16
!SFX2 = #$19
3) SFX1 corresponds to when you're charging. SFX2 corresponds to when you're charged. So change the value for SFX2 to #$00 (so no sound plays when you're fully charged).
4) The magic here happens in SFX1. Using the link provided below, look through the sound effects listed under $7E:1DF9. Choose a sound effect that'll loop quickly (for a d-d-d-d-d-d-d sound), then end with the full sound effect.
Personally, I chose sound effect 0D, so once my character's charged up it plays the "Get Cape" sound, then ends. This way, the background music can still be heard while you're character's charged.
That's my solution, anyway. A very "A to B" answer for a small question. The sound effect list is below:
Looking for high quality rips from our Grand Dad SiIvaGunner for my hack. Much appreciation to anyone who links me to any (besides Athletic PAL).