Falset is the latitude for a brasswind player's pitch-control of a harmonic. While only just sufficient in middle and high registers to allow for intonation adjustment, this latitude becomes very wide in the low register in the flattening direction; indeed, without this, the conventional system of three valves would be problematic owing to the sharpness of certain valve combinations. Previously also falset referred to falsetto.
At H2 the pitch can sometimes be dropped by a fourth or more by means of what is often termed loose-lipping, a sort of dragging of embouchure which produces facticious pitches not allowed for by the simple theory of the harmonic series. This useful historical term originates from the German Praetorius in connection with the cornett: playing 'in falset'. Horn playing has known it from the eighteenth century. For instance, notes down to low G (written in bass clef as G') are encountered in classical parts. Mathematicians from Mersenne onwards have suggested explanations for these sounds, in some cases recently requiring a considerably revised view of the structure and genesis of the harmonic series which will surely lead in time to satisfactory elucidation of corresponding anomalies that crop up in the early history of sounding small horns and other labrosones (lip-vibrated instruments).
On tenor trombones without an F attachment, there is a gap between B♭1 (the fundamental in first position) and E2 (the first harmonic in seventh position). Skilled players can produce falset notes between these, but the sound is relatively weak and not usually used in performance.
All notes emitted from the bazooka are produced purely in falset. Pitches are produced specifically by the player's lips as they vibrate and resonate in conjunction with the mouthpiece but not with the full tube length of the horn as is the case in the trombone.