The SPC700 runs independently from the main system so for sound there is no speed difference whatsoever between NTSC and PAL (was fun playing the imported Mario RPG and watching a silent staff roll as the piece already ended while the game was tugging behind at PAL speed ^^).
For SPC, the only time the PAL version would sound slower than NTSC or vice versa was if the music was also somehow processed by the SNES as well (hence the "undumpable" games). Even with those games which have a PAL release, they were usually fixed as well. The Chessmaster's music actually sounds at a slower tempo in the PAL version than in the NTSC version for this reason. However, as for NSFs, you can play the music at PAL speed with NEStopia by selecting the region to be PAL instead of Auto or NTSC. MrNorbert1994 also has ripped the PAL version of many (but not all, as some PAL versions of games are still missing such as Metroid) games that were released in NTSC as well, and those can be found in his gigantic NSF archive on his website. I think VGMs only play at a recorded locked speed of 44100hz (not PCM, but the speed of each note somehow) which is simply captured from whichever TV mode is outputted, so I think VGMs simply need to be re-ripped if they're not already PAL. However, I could be wrong, as I don't know too much about the VGM format.
Will for vgm format for winamp you can change the speed from ntsc to pal, i wonder if you can do it for the foobar plugins for nsf and vgm and I'll check if any snes game music ran slow on pal systems