Col Legno (meaning ‘with the wood’) is a special technique where the main wooden stick of the bow is tapped against the string – this percussive effect is rarely used but can have a distinctive sound when used in an orchestra or string section.
Col Legno is even less commonly used for a solo instrument and therefore it is at it’s most effective when a large group of players are doing it simultaneously.
Pieces to listen to that use Col Legno to great effect are Saint Saens’ ‘Danse Macabre’ where it is used to suggest the rattling of skeletons and also in Berlioz’s ‘Symphony Fantastique’ to represent the Dream of the Witches Sabbath, thirdly it is heard in Mars from Holst’s ‘Planets Suite’.
Some string players are nervous of using the technique as it can create scratch marks on the back of a valuable pernambuco bow, however when used as Col Legno Tratto, the sound is very quiet and yet the pitch of the note is still evident with very little risk of damage to an expensive bow!