arco explained
A direction to resume playing with the bow after a pizzicato passage on a string instrument
In Depth
Arco is the Italian word for bow. When written in a part, it tells the player to return to bowing after a passage of pizzicato (plucking). The notation is necessary because the default playing position for all bowed string instruments is with the bow, and any departure from this default needs to be both indicated (pizzicato) and cancelled (arco). The transition from pizzicato to arco requires a brief moment for the player to reposition the bow.
Orchestral string players develop the ability to switch between arco and pizzicato in fractions of a second — a skill that audiences rarely notice but that requires years to perfect.