Background music that plays while the focus is on Blake tends to be played with piano.
Roman Torchwick has a sinister violin and piano piece that plays when he appears.
"I Burn" is this for Yang, basically being a long Badass Boast in song form. So far, it's been remixed three times in Volume 3: a smooth jazz version when she took out Team FNKI, a badass techno version in her fight against Mercury, and a sad piano version as she was being arrested on television for "breaking" Mercury's leg.
Cinder's appearances are accompanied by a low choir, often complemented by a rising scare chord and heavy percussion. Generally speaking, her theme gets fuller, longer, and more intense the closer she gets to her goal, with long notes typically becoming shorter, sharper ones when in combat or as she nears her victory in the volume 3 finale.
Whenever things get deep around Dictator Pickles in Alfred's Playhouse, II. Allegretto by Zagreb Philharmonic Orchestra can be heard growing in the background. Labby also has a dark organ tune follow him in The Movie.