B♭ major
Key with two flats in its signature (German: B-Dur).
What it means
B♭ major is the major key with two flats in its signature, namely B♭ and E♭. Its tonic is the note that German usage calls b — the note English names B flat. Here lies the best-known trap of German note-naming: English B corresponds to German H, which is why in German this key is called B-Dur, while its English name is B♭ major. A German source’s B always means B♭; its H means English B.
Musical use
Its relative minor is G minor, which bears the same signature. On the circle of fifths B♭ major lies two steps on the flat side, between F major and E♭ major.
In practice this key is of particular importance for wind players. Clarinet, trumpet, tenor horn and soprano saxophone are pitched in B♭ and sound a whole tone lower than notated; their parts are written transposed accordingly. For wind bands and brass bands B♭ major and the neighbouring flat keys are therefore the most comfortable, which is reflected throughout the repertoire of these ensembles. For string players too B♭ major lies usable, though less favourably than the sharp keys, because fewer open strings are available.
In unequal temperaments each key had a character of its own, and the historical talk of key characters refers to this circumstance; in equal temperament all keys sound the same, and differences arise only from the position on the particular instrument.
Because of the tuning of the brass instruments and clarinets, B♭ major is a favoured key of wind music; trumpet, clarinet and tenor horn frequently stand in B♭, so that their parts lie especially well in this key. In jazz and big-band literature too B♭ major is widespread. On the circle of fifths B♭ major stands between F major and E♭ major; its relative minor is G minor, its parallel minor B♭ minor with five accidentals. The accidentals are B♭ and E♭.
Performance practice
Say the two flats aloud before the first note and name the notes affected. When working with English-speaking musicians watch for the differing designation. And with transposing instruments check whether you mean the written or the sounding key.