Hello I am new to this whole rom hacking thing but I always wanted to make my own music. I tried for almost 3 hours and I had no luck, could someone teach me or help me make some songs for mega man 3? They wouldn't be custom but songs from different existing nes games like Castlevania 3, Mario bros, Contra, Etc.
This forum is not really geared towards ROM hacking, but you might find
this useful.
It's important to note that each NES have uses a different music engine, so porting music from one game to another isn't as simple as it sounds. As I see it, your options are:
1- Study the target game's music engine thoroughly and rewrite the songs for this engine manually. Not all features are available in all engines, so the songs may end up sounding differently;
2- Expand the size of the target ROM (may require a mapper hack if the current mapper's capacity is already maxed out) to include multiple playback engines, ported from other games. Managing the RAM requirements of multiple music engines and handling sound effects would be quite a challenge, even for experienced programmers.