Pitch bends & glissandi
The easiest way to produce an alteration in pitch over a small interval is through the use of pitch bends. Notes on the alto flute may be altered varying amounts from microtonal increments to a semitone or even in some cases a tone, up and down, depending on the note chosen. A fingering which uses more closed keys (such as d'' or c') has less pitch flexibility than one using an open tube (such as c sharp''). There is generally more flexibility when bending a pitch downwards than there is going up, and the highest register has the smallest amount of pitch flexibility.
A pitch bend is created by rolling the flute inwards (for lower pitch) or outwards (for higher pitch), in combination with movements of the player's head, embouchure and jaw in order to create the maximum alteration in air angle. It should be noted that the further the air stream moves from normal playing position, the more diminished the dynamic control is, with the resultant sound becoming gradually quieter and with a progressively thinner tone.
The video clip shows pitch bends on c#'' and d'. The c#'', which uses a fully open tube, has much more flexibility than the d', which has most of the keys closed.
Pure glissandi can be produced through finger movements. Upwards glissandi may be produced throughout the range of the instrument by sliding off open holes and gently depressing levers. The evenness of the intervals is determined by the pitch range required; short pitch range glissandi on open holed keys are most successful and reliable.
Downwards glissandi are more difficult to control as this relies on closing the keys evenly enough not to create a bump in the sound. For short interval ranges, pitch bends are most reliable.
Non-pure glissandi can be played as rapid scales in a particular key, or chromatic. Since the choice of scale can often be ambiguous, particularly in contemporary music, it is advisable to notate this instead as a run of grace notes. The effect in performance will be the same, but the composer has greater control over the pitches used.
This is predominantly a jazz effect at the end of a phrase, where a player will begin a rapid descending scale in the appropriate key, while also executing a diminuendo to nothing.
The examples below show various notational possibilities for pitch bends. In the first example, lines give an indication of the required pitch. These are specified further in the second example through the use of noteheads and accidentals.
Glissandi can be shown either with the standard glissando sign, or through the use of grace notes to give more detailed specification of pitch.