A general comment regarding extended techniques:
Scordatura tuning
Retuning the strings. Notated with a verbal instruction to retune, possibly with an additional staff to show new tunings. Do not retune more than a tone, and in general it is better to lower than raise the pitch of the string. Retuning takes time and care.
Tap instrument
Tapping the body of the instrument with fingers or with the bow. Notated with a verbal instruction, with x-shaped noteheads for extended passages. Finger taps are common, but bow taps are to be used with care: no player would want to risk damaging the violin. If a bow tap is called for, the safest place to tap is the chinrest.
Play behind bridge
Playing the strings between the bridge and the tailpiece. Notated with a verbal instruction, with x-shaped noteheads if necessary. The standard bowing and plucking techniques may be used for this effect.
Bow on bridge
Bowing the strings directly on the bridge. Notated with a verbal instruction, with x-shaped noteheads if necessary. This is not the same as sul ponticello which plays near the bridge.
Bow tailpiece
Bowing the tailpiece. Notated with a verbal instruction. Extremely quiet!
Strike strings
Striking the strings with the hand. Notated with a verbal instruction. Pitches may also be fingered with the left hand.
Scratch note
Pressing down hard on the string with the bow to produce a rasping. Notated with a verbal instruction, with x-shaped noteheads. As an obvious sign of bad technique, this sound is not flattering to the player.
'Silent' fingering
Fingering pitches with the left hand without bowing or plucking the strings. Notated with a verbal instruction. Very quiet.
