sul tasto
Bowing over the fingerboard, producing a soft, flute-like tone.
In Depth
Sul tasto means over the fingerboard — the player bows over the fingerboard rather than in the normal position between the fingerboard and bridge. This produces a soft, breathy, flute-like tone with fewer overtones than normal bowing, creating a gentle, ethereal quality.
The technique is the opposite of sul ponticello (near the bridge). Debussy and other Impressionist composers used sul tasto extensively to create delicate, floating textures. The softer tone blends beautifully with sustained wind instruments and harp. Marked as sur la touche in French scores, the technique requires careful bow control since the string offers less resistance over the fingerboard.
Debussy specified sul tasto in his String Quartet to create the soft, floating textures that define Impressionist chamber music — the technique became his sonic signature for strings.