With the bow
"Arco" is an Italian term used in music, particularly in relation to string instruments such as the violin, viola, cello, and double bass. It translates to "with the bow" in English. When a musician is instructed to play "arco", it means that they should use the bow to produce sound from the instrument, as opposed to other techniques like pizzicato (plucking the strings with the fingers).
Playing arco involves drawing the bow across the strings with varying degrees of pressure, speed, and direction to produce different tones and articulations. The bow is typically held in the right hand of the player and is made up of a stick (usually made of wood) and horsehair stretched between the two ends. By adjusting the pressure and speed of the bow, musicians can create a wide range of expressive and dynamic effects.
Arco technique is fundamental to the performance of string instruments and allows for the sustained and melodic qualities associated with these instruments. It enables musicians to produce a smooth and connected sound, as well as execute techniques such as legato (smooth and connected playing), staccato (short and detached notes), and various bowing articulations like spiccato, martelé, and sautillé.
The use of arco technique is indicated in sheet music by the term "arco" placed above or below the staff. Conversely, when a composer or arranger wants the musician to switch from arco to a different technique, they may use terms like "pizzicato" or "col legno" (using the wood of the bow to strike the strings).