Intonation (music)

Intonation, in music, is a musician's realization of pitch accuracy, or the pitch accuracy of a musical instrument. Intonation may be flat, sharp, or both, successively or simultaneously.

The lower or upper pitch of an interval may be sharp or flat, or both pitches of an interval may be out of tune.

If the lower pitch is sharp or the upper pitch is flat, the interval may be said to be flat given that as a whole it is too narrow; while if the lower pitch is flat or the upper pitch is sharp, the interval may be said to be sharp given that as a whole it is too wide. Intervals are conventionally measured from the bottom, as such in an interval that is too wide the upper pitch is thus sharp. For example, the "flat fifth" of meantone temperament.

However, the interval itself may be in tune, in relation to itself (i.e. both notes of the interval are in tune in relation to each other), but flat or sharp as a whole and thus both notes of the interval is out of tune.

A melody or harmony is flat or sharp if it is too low or high, respectively. A melody may be successively both sharp and flat. A harmony may be simultaneously and successively both sharp and flat.

With fretless string instruments such as violins or cellos, intonation depends on the exact places the musician's fingers press the strings against the instrument's fingerboard, as well as any pull or push the musician exerts on the string, either along the string's length or perpendicular to it.

The pleasantly "alive" sound of a large string section results from the amount by which each stringed instrument is slightly out of tune.

Several factors affect fretted instrument intonation, including depth of the string slots in the nut, bridge saddle position, the position of the frets themselves, and the technique of the musician.

On fretted string instruments, pushing a string against a fret—aside from raising the string's pitch because it shortens the string—also causes a slight secondary raise in pitch because pushing the string increases its tension. If the instrument doesn't compensate for this with a slight increase in the distance from the bridge saddle to the fret, the note sounds sharp.

Most electric fretted string instruments have individually adjustable bridge saddles, adjustable with a screw driver or Allen wrench. Acoustic fretted instruments typically have either a floating bridge, held in place by string tension, or a fixed bridge, such as a pin bridge on an acoustic guitar. A luthier or technician adjusts a floating bridge simply by carefully changing its position until the intonation is correct. Adjusting intonation on a fixed bridge involves carefully shaping the bridge saddle with a file to alter the string's contact point.

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