I don't know if this thread has been entirely derailed to the point that no one will see this, but here we go.
ALRIGHT, I just took a gangder at the SNDInfo in the Musics .PK3, and was suprised to see that it hadn't really been updated since V3A, meaning none of the non-MM8 Wily musics are balanced by it. There were catagories for MM&B as well as the Wily Tower, but they're empty.

No wonder the new music is as quiet as it is. :?
A few of the new weapons are also rather quiet, as a side note.Anyway, here's my personal SNDInfo fix, 'cause why not. It's just a small edit of the original, but everything rather even leveled.
//MM1
$musicvolume ELEMUS 1.0
$musicvolume CUTMUS 0.95
$musicvolume FIRMUS 1.0
$musicvolume BOMMUS 0.9
$musicvolume ICEMUS 0.95
$musicvolume GUTMUS 0.9
$musicvolume OILMUS 1.1
$musicvolume TIMMUS 1.1
$musicvolume 1DW1MUS 1.0
$musicvolume 1DW2MUS 1.0
$musicvolume MM1BOSS 0.9
$musicvolume MM1PBOSS 1.0
$musicvolume MM1WBOSS 0.9
$musicvolume DRLIGHT 1.0
//MM2
$musicvolume D_DM2TTL 0.9
$musicvolume AIRMUS 0.9
$musicvolume BUBMUS 1.0
$musicvolume CRAMUS 1.05
$musicvolume FLAMUS 0.9
$musicvolume HEAMUS 0.9
$musicvolume METMUS 0.9
$musicvolume QUIMUS 0.9
$musicvolume WOOMUS 0.9
$musicvolume 2DW1MUS 0.9
$musicvolume MM2BOSS 0.9
$musicvolume D_DM2INT 0.9
//MM3
$musicvolume MM3GO 1.0
$musicvolume GEMMUS 1.0
$musicvolume HARMUS 1.0
$musicvolume MAGMUS 1.0
$musicvolume NEEMUS 1.0
$musicvolume SHAMUS 1.0
$musicvolume SNAMUS 1.0
$musicvolume SPAMUS 1.0
$musicvolume TOPMUS 1.0
$musicvolume 3DW2MUS 1.0
$musicvolume MM3BOSS 1.0
$musicvolume MM3BOSS2 1.0
$musicvolume MM3SEL 1.0
//MM4
$musicvolume MM4GO 1.0
$musicvolume DRIMUS 1.0
$musicvolume DUSMUS 1.0
$musicvolume SKUMUS 1.0
$musicvolume TOAMUS 1.0
$musicvolume RINMUS 1.0
$musicvolume DIVMUS 1.0
$musicvolume BRIMUS 1.0
$musicvolume PHAMUS 1.0
$musicvolume 4DC2MUS 1.0
$musicvolume MM4BOSS 1.0
$musicvolume MM4BOSS2 1.0
$musicvolume GAMEWIN 1.0
//MM5
$musicvolume GYRMUS 1.1
$musicvolume WAVMUS 1.1
$musicvolume NAPMUS 1.05
$musicvolume GRAMUS 1.05
$musicvolume CRYMUS 1.05
$musicvolume CHAMUS 1.05
$musicvolume STAMUS 1.05
$musicvolume STOMUS 1.1
$musicvolume DARMUS 1.05
$musicvolume MM5BOSS 1.05
$musicvolume DRBMUS 1.05
//MM6
$musicvolume FLMMUS 1.0
$musicvolume BLIMUS 1.0
$musicvolume CENMUS 1.0
$musicvolume KNIMUS 1.0
$musicvolume PLAMUS 1.0
$musicvolume TOMMUS 1.0
$musicvolume WNDMUS 1.0
$musicvolume YAMMUS 1.0
$musicvolume MRXMUS 1.0
$musicvolume MM6BOSS 1.0
$musicvolume MM6BOSS2 1.0
$musicvolume TORNWIN 1.0
$musicvolume NEWINT 1.0
//MM7
$musicvolume SPRMUS 1.1
$musicvolume TURMUS 1.1
$musicvolume BURMUS 1.1
$musicvolume CLOMUS 1.1
$musicvolume FREMUS 1.0
$musicvolume SDEMUS 1.15
$musicvolume SLAMUS 1.1
$musicvolume JUNMUS 1.1
$musicvolume MM7BOSS 1.35
$musicvolume 7DW1MUS 1.2
$musicvolume 7DW2MUS 1.5
$musicvolume 7DW3MUS 1.1
$musicvolume 7DW4MUS 1.0
$musicvolume MM7OBOS 1.1
$musicvolume MM7FBOS 1.2
$musicvolume MM7VIC 1.2
$musicvolume MM7END 1.25
//MM8
$musicvolume SWOMUS 1.0
$musicvolume TENMUS 1.0
$musicvolume TENMUS2 1.0
$musicvolume TENVMUS 1.0
$musicvolume AQUMUS 1.0
$musicvolume ASTMUS 1.0
$musicvolume CLNMUS 0.95
$musicvolume SEAMUS 0.9
$musicvolume FROMUS 1.0
$musicvolume GREMUS 1.0
$musicvolume DUOMUS 1.0
$musicvolume MM8BOSS 1.0
$musicvolume 8DW1MUS 1.0
$musicvolume 8DW2MUS 1.0
$musicvolume 8DW3MUS 1.0
$musicvolume 8DW4MUS 1.0
$musicvolume ERBATTLE 1.0
$musicvolume CREDMUS2 1.0
//MM&B
$musicvolume MUSUS 1.3
$musicvolume ASTMUS2 1.2
$musicvolume TENMUS3 1.3
$musicvolume COLMUS 1.3
$musicvolume DYNMUS 1.3
$musicvolume PIRMUS 1.3
$musicvolume BRNMUS 1.3
$musicvolume GROMUS 1.3
$musicvolume MGCMUS 1.3
$musicvolume KINMUS 1.3
$musicvolume BDWMUS 1.3
$musicvolume MMBKING 1.3
$musicvolume MMBDW 1.3
$musicvolume MMBBOSS 1.1
$musicvolume MMBOBOS 1.3
//Wily Tower
$musicvolume BRGMUS 1.3
$musicvolume MWSMUS 1.1
$musicvolume HSHMUS 1.1
$musicvolume WTDW1MUS 1.2
$musicvolume WTDW4MUS 1.2
$musicvolume MMWTBOSS 1.2
$musicvolume MMWTFBOS 1.2
$musicvolume WTWIN 1.1
$musicvolume MMWCRE 1.1
//MM9
$musicvolume CREDMUS 0.4
$musicvolume ENDMUS 0.4
//MM10
$musicvolume WILYCRI 0.65
$musicvolume TOGETH 0.65
$musicvolume BALMUS 0.7
$musicvolume ENKMUS 0.7
$musicvolume PUNMUS 0.72
$musicvolume MM10RAIN 0.7
$musicvolume MM10FB1 0.6
$musicvolume MM10FB2 0.6
$musicvolume FINAMUS 0.6
$musicvolume STATIK 0.6
//CTF
$musicvolume CTFMUS1 0.7
$musicvolume CTFMUS2 0.7
$musicvolume CTFMUS3 0.7
$musicvolume CTFMUS4 0.8
$musicvolume CTFMUS5 1.2
$musicvolume CTFMUS6 1.35
$musicvolume CTFMUS7 0.85
$musicvolume CTFMUS8 0.75
$musicvolume CTFMUS9 0.7
$musicvolume CTFMUS10 0.85
$musicvolume CTFMUS11 1.0
$musicvolume CTFMUS12 1.0
$musicvolume CTFMUS13 1.0
$musicvolume CTFMUS14 1.15
$musicvolume CTFMUS15 1.0
$musicvolume CTFMUS16 1.0
$musicvolume CTFMUS17 1.0
$musicvolume CTFMUS18 1.0
$musicvolume CTFMUS19 1.0
$musicvolume CTFMUS20 1.0
//Special
$musicvolume GHOULS 0.9
$musicvolume D_TTFTW 0.9
//Victory
$musicvolume MM1VIC 0.9
$musicvolume MM2VIC 0.9
$musicvolume MM3VIC 0.9
$musicvolume MM4VIC 0.9
$musicvolume MM7VIC 0.9
$musicvolume MMWTVIC 1.0
$musicvolume COSVIC 1.0
$musicvolume WILYVIC 0.9
Additionally, why are King and Wily's MM&B themes refered to as "MMBKING" and "MMBDW" rather than "KINMUS"/"KINGMUS" and "BDWMUS"/"BDW1MUS"?