Altered Beast (Power Up) plays on each stage after you've collected enough orbs and morphed into an animal.
This song is the second half of part 1 of track 2 on the album the album Galaxy Force. It's also track 3 on Sega System 16: Complete Soundtrack Vol.2. The title on both albums is "Altered Beast", but only the later album affixes the "(Power Up)" subtitle, and that is assumed to be correct.
Games
Altered Beast (ARC)
This is the original composition of Altered Beast as composed by Tohru Nakabayashi.
The song plays on a YM2151 and is internal song number 0x91.
Altered Beast (GEN)
The Genesis version plays on the YM2612.
Altered Beast (SMS)
Like the original game, the Master System and Mark III release of Altered Beast plays Altered Beast for the music after a player transforms into a werewolf, but unlike the arcade game, it only plays the song for the werewolf and gold wolf. For the dragon and weretiger transformations, they play the Gaum-Hermer (Boss Theme).
The Master System release of Altered Beast plays the song on the SN76489, but Mark III plays on the YM2413.
Links