Action (music)

The action of a stringed instrument is the distance between the fingerboard and the string, which determines how easy it is to sound notes when pressure is applied with the finger tips. Generally a low action is considered to be more playable, due to the lower amount of pressure needed to press the string to the fingerboard. However, if the action is set too low the instrument could suffer from an unwanted buzzing noise (on fretted instruments, this is known as fret buzz). Conversely, if the action is too high, then the strings may become taut and difficult, if not impossible, to press down without breaking.

Guitars

On some instruments, such as certain guitars, the action can be easily adjusted by tightening screws at the bridge which changes the height of the strings. On other instruments, changing the action can be potentially more complicated and involve removing entire pieces from the instrument to achieve desired action.

Tune-o-matic bridges

These bridges use small thumbwheels to raise or lower the bridge; sometimes these are accompanied or replaced by flat-head screw fitting.

The action on a guitar is also slightly affected by the adjustment of the truss rod. Tightening the truss rod gives the neck a backward bow and tends to lower the action, and loosening the rod gives the neck a forward bow, giving a higher action.

It is recommended that the action on an electric guitar should be within 0.5mm of 1.8mm on the high E string and 2.4 on the low E string when in standard tuning.

(Note: it's better to have a slight forward bow to the guitar to allow the strings to vibrate well. Adjustment of the action should be done on the bridge of the guitar.)