An aux send, also known as an auxiliary send, is a feature found on most mixing consoles and digital audio workstations (DAWs) that allows an audio signal to be sent from one channel to an auxiliary (aux) bus or channel. This is typically used to add effects or processing to a specific channel or group of channels without affecting the entire mix.

When an aux send is used, a portion of the signal from the original channel is sent to the aux bus or channel, where it can be processed separately. This can be used to apply effects like reverb or delay to a specific instrument or group of instruments or to send a signal to an external effects processor like a hardware reverb unit.

The amount of signal sent to the aux bus or channel is typically controlled by an aux send knob or fader on the original channel, and the level of the processed signal can be adjusted using the aux return knob or fader on the aux channel.

Overall, the use of aux sends can be a powerful tool in music production, allowing producers and engineers to add depth and dimension to their mixes by applying specific effects to individual channels or groups of channels.