We transcribe the parts as they sound on the original recording. Some songs may have used 5 string Bass Guitars utilising the whole range down to low B below the bass stave. If your Bass player only has a 4 string Bass Guitar they will not be able to play notes below a low E, therefore we have written the parts up an octave where required to enable 4 String bass players to comfortably play the music.
As we offer multiple keys the transposition could also lower the pitch below that of normal 4 string basses. Choose the bass type that suits your needs.