Col Legno

What it is: Striking or dragging the string with the wooden back of the bow instead of the hair. Two distinct techniques share the name:

Col legno battuto — struck with the wood. Percussive, clicking attack.
Col legno tratto — dragged with the wood. Whispery, hollow tone.

What it sounds like: Battuto is dry and percussive — like a wood block. Tratto is veiled and ghostly — like a string instrument heard through a wall. Both are color effects, not loud or expressive sounds.

When to use it: When you want strings to function as percussion (battuto) or as a ghostly, otherworldly texture (tratto). Distinctive enough that it announces itself — use sparingly so the effect doesn't wear out.

Tip: Players are reluctant to use col legno on expensive bows. The wood gets damaged over time. For an entire orchestral section, the conductor may opt to use student bows for that passage. Don't ask for col legno casually — it's a "we really need this" effect.

Listen: Berlioz, Symphonie fantastique, 5th movement (Songe d'une nuit du sabbat) — the col legno passage in the Dies irae section is the canonical example. Holst, The Planets, "Mars" — col legno violin and viola figurations.