Concert pitch vs written pitch: transposing instruments, with audio

What concert pitch and written pitch mean

Concert pitch is the pitch that actually sounds. It is the same pitch on a piano, a guitar or a flute, and the same pitch everyone in the room hears, no matter which instrument produced it.

Written pitch is the note printed on a player's part. For most instruments the two are the same: middle C on a flute part sounds middle C. But clarinet, trumpet, saxophone and horn are transposing instruments: the note on the page and the pitch that comes out are a fixed interval apart. A B♭ clarinet reading a written C actually sounds B♭, a step below.

This is not a quirk or an error. It exists because of how each instrument's tubing and fingerings work: instruments in the same family (say, the clarinet and its bass cousin) can share one set of fingerings if their parts are written a fixed distance apart, even though the actual pitch produced is different. The player learns one fingering chart; the composer and arranger do the transposing on paper instead.

A concert B♭ major chord, written for a full band, ends up printed as C major for the clarinets and trumpets, G major for the alto sax, and F major for the horn, each shifted by that instrument's own interval, so that everyone still plays the fingering pattern they know while the chord that comes out is the same B♭ major for everyone in the room.