Bechstein is a type of piano, and debauchery is defined as such:
de·bauch·er·y P Pronunciation Key (d-bôch-r)
n. pl. de·bauch·er·ies
Extreme indulgence in sensual pleasures; dissipation.
debaucheries Orgies.
Archaic. Seduction from morality, allegiance, or duty.
So it's really just saying "indulgent piano playing by Freddie".