Why a shift is sometimes needed

A B♭ instrument sounds a whole step lower than it is written: a written C comes out as B♭. Backing tracks are in concert pitch, the sound that comes out. So if your part is already written for your instrument, the track and the part fit, and nothing needs to move.

You read…Set Key to
a part written for your B♭ instrument0
a concert-pitch chart, played as written−2

The second row in words

If you play a concert-pitch chart without transposing it, your instrument sounds a whole step below the chart. To bring the track to that same lower key, lower it by 2 semitones: press − beside Key twice.

And the other way round

A player of a C instrument, such as flute or piano, who reads a part written for B♭ is in the opposite position: the written notes sound a whole step above the track, so the track goes up by 2 instead. For you, on the B♭ instrument itself, the answer is 0 or −2.

Choosing a friendlier key

A concert key with many sharps becomes an even sharper key on the page of a B♭ instrument, because written keys sit a whole step higher. If the written part is hard to read, shift the track by one or two semitones to a nearby key that looks simpler, and practice there.

A worked example

A concert-pitch chart says the tune is in G, and the backing track is in G. On your trumpet you play the written notes of G major without transposing them, which sounds as F major. Lower the track by 2 semitones, from G to F, and the two agree.