[Listening extract audio not available in printed QP] A string quartet uses three techniques: a clip on the bridge to muffle the sound, striking strings wit...

(a) Con sordino [1]

Con sordino is the Italian instruction meaning "with mute." When applied to string instruments, it tells the player to attach a small device called a mute (sordino) to the bridge of the instrument. The mute dampens the vibrations of the bridge, reducing the volume and producing a softer, more veiled, and slightly nasal tone colour. This is the technique used when the question describes a "clip on the bridge to muffle the sound." The opposite instruction, senza sordino, tells the player to remove the mute. String mutes are typically small clamps made of rubber, metal, or leather.

(b) Col legno [1]

Col legno (Italian for "with the wood") is a string technique in which the player strikes or bounces the strings with the wooden stick of the bow rather than drawing the hair across them. This produces a dry, clicking, percussive sound that is very different from the normal bowed tone. Col legno is used for special effects in orchestral writing - notable examples include the "March to the Scaffold" from Berlioz's Symphonie fantastique and the "Danse macabre" by Saint-Saens. There are two variants: col legno battuto (striking) and col legno tratto (drawing the wood along the string).

(c) Double stopping [1]

Double stopping is the technique of bowing two strings simultaneously, producing two notes at once. The player presses down on two adjacent strings and draws the bow across both, creating a harmonic interval or chord. This enriches the texture by allowing a single string player to produce harmony rather than just a single melodic line. Triple stopping (three strings) and quadruple stopping (four strings) are also possible, though sustained chords on more than two strings require the bow to roll quickly across the strings due to the curvature of the bridge. Double stopping is used extensively in solo violin repertoire and in orchestral passages requiring a fuller sound from the string section.