▁That ▁Bach ▁saw ▁the ▁six ▁parts ▁as ▁compr ising ▁a ▁greater , ▁un ified ▁whole ▁is ▁evident ▁both ▁from ▁the ▁surv iving ▁printed ▁text ▁and ▁from ▁the ▁structure ▁of ▁the ▁music ▁itself . ▁The ▁edition ▁has ▁not ▁only ▁a ▁title — We i hn ach ts - Or ator ium — connect ing ▁together ▁the ▁six ▁sections , ▁but ▁these ▁sections ▁are ▁also ▁number ed ▁consec ut ively . ▁As ▁John ▁But t ▁has ▁mentioned , ▁this ▁points , ▁as ▁in ▁the ▁Mass ▁in ▁B ▁minor , ▁to ▁a ▁unity ▁beyond ▁the ▁performance ▁constraints ▁of ▁the ▁church ▁year . ▁ ▁Music ▁Bach ▁express es ▁the ▁unity ▁of ▁the ▁whole ▁work ▁within ▁the ▁music ▁itself , ▁in ▁part ▁through ▁his ▁use ▁of ▁key ▁sign atures . ▁Part s ▁I ▁and ▁III ▁are ▁written ▁in ▁the ▁keys ▁of ▁D ▁major , ▁part ▁II ▁in ▁its ▁sub domin ant ▁key ▁G ▁major . ▁Part s ▁I ▁and ▁III ▁are ▁similarly ▁scored ▁for ▁ex uber ant ▁tr ump ets , ▁while ▁the ▁Past oral ▁Part ▁II ▁( refer ring ▁to ▁the ▁She ph erd s ) ▁is , ▁by ▁contrast , ▁scored ▁for ▁wood wind ▁instruments ▁and ▁does ▁not ▁include ▁an ▁opening ▁ch orus . ▁Part ▁IV ▁is ▁written ▁in ▁F ▁major ▁( the ▁relative ▁key ▁to ▁D ▁minor ) ▁and ▁marks ▁the ▁fur th est ▁musical ▁point ▁away ▁from ▁the ▁or atorio ' s ▁opening ▁key , ▁scored ▁for ▁horn s . ▁Bach ▁then ▁emb arks ▁upon ▁a ▁journey ▁back ▁to ▁the ▁opening ▁key , ▁via