String instrument
Contact points along the string

In bowed instruments, the bow is normally placed perpendicularly to the string, at a point halfway between the end of the fingerboard and the bridge. However, different bow placements can be selected to change timbre. Application of the bow close to the bridge (known as sul ponticello) produces an intense, sometimes harsh sound, which acoustically emphasizes the upper harmonics. Bowing above the fingerboard (sul tasto) produces a purer tone with less overtone strength, emphasizing the fundamental, also known as flautando, since it sounds less reedy and more flute-like.

Bowed instruments pose a challenge to instrument builders, as compared with instruments that are only plucked (e.g., guitar), because on bowed instruments, the musician must be able to play one string at a time if they wish. As such, a bowed instrument must have a curved bridge that makes the "outer" strings lower in height than the "inner" strings. With such a curved bridge, the player can select one string at a time to play. On guitars and lutes, the bridge can be flat, because the strings are played by plucking them with the fingers, fingernails or a pick; by moving the fingers or pick to different positions, the player can play different strings. On bowed instruments, the need to play strings individually with the bow also limits the number of strings to about six or seven strings; with more strings, it would be impossible to select individual strings to bow. (Note: bowed strings can also play two bowed notes on two different strings at the same time, a technique called a double stop.) Indeed, on the orchestral string section instruments, four strings are the norm, with the exception of five strings used on some double basses. In contrast, with stringed keyboard instruments, 88 courses are used on a piano, and even though these strings are arranged on a flat bridge, the mechanism can play any of the notes individually.

Similar timbral distinctions are also possible with plucked string instruments by selecting an appropriate plucking point, although the difference is perhaps more subtle.

In keyboard instruments, the contact point along the string (whether this be hammer, tangent, or plectrum) is a choice made by the instrument designer. Builders use a combination of experience and acoustic theory to establish the right set of contact points.

In harpsichords, often there are two sets of strings of equal length. These "choirs" usually differ in their plucking points. One choir has a "normal" plucking point, producing a canonical harpsichord sound; the other has a plucking point close to the bridge, producing a reedier "nasal" sound rich in upper harmonics.
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