Editing Vibrato (section)

==Acoustic basis==
The use of vibrato is intended to add warmth to a note. In the case of many [[string instrument]]s the sound emitted is strongly directional, particularly at high frequencies, and the slight variations in pitch typical of vibrato playing can cause large changes in the directional patterns of the radiated sound.<ref>{{cite web | last=Curtin | first=Joseph | title=Weinreich and Directional Tone Colour | url=http://josephcurtinstudios.com/article/the-violin-finally-speaks/ | date=April 2000 | work=Strad Magazine | access-date=2009-05-23 | quote=In the case of string instruments, however, not only are they strongly directional, but the pattern of their directionality changes very rapidly with frequency. If you think of that pattern at a given frequency as beacons of sound, like the quills of a porcupine, then even the slight changes in pitch created by vibrato can cause those quills to be continually undulating. | archive-url=https://web.archive.org/web/20141229211555/http://josephcurtinstudios.com/article/the-violin-finally-speaks/ | archive-date=2014-12-29 | url-status=dead }}</ref> This can add a shimmer to the sound; with a well-made instrument it may also help a solo player to be heard more clearly when playing with a large orchestra.<ref>{{cite web |url=http://www.schleske.de/en/our-research/handbook-violinacoustics/vibrato-of-the-musician.html |title=The psychoacoustic secret of vibrato |first=Martin |last=Schleske |access-date=11 February 2010 |quote=The “fiery tone” that likely results from this phenomenon is an essential characteristic of good violins. }}</ref>

This directional effect is intended to interact with the room acoustics to add interest to the sound, in much the same way as an acoustic guitarist may swing the box around on a final sustain, or the rotating baffle of a [[Leslie speaker]] will spin the sound around the room.