Volume swell

:"For other uses, see crescendo."A volume swell is a musical crescendo commonly associated with the electric guitar.

Roughly speaking, the sound of a guitar note is characterised by an initial 'attack' where the pick or nail produces higher pitched overtones over the top of the fundamental note, followed by a diminution of these overtones. Consequently, the end of the note is softer than the attack. Volume swells alter the tone of the note, reducing the trebly tone of the attack and allowing the softer tone that follows to sustain.

The technique is often executed by the little finger of the guitarist which is wrapped around the volume pot of the guitar. When the note is struck the volume is increased from zero by a rolling motion of the little finger. Alternatively, the effect is achieved with a volume pedal. It is sometimes called "violinning", because the sound is similar to a bowed violin. Allan Holdsworth pionered the technique of the pedal swelling along with a delay unit to create a thicker sound that's more associated with cellos.

Roy Buchanan was famous for his emotive volume swells, often in combination with note bending and vibrato. Jan Akkerman used the technique with Focus.

Another early use of swells is found in the Beatles recording of Eight Days a Week.