Pro Tools lets you discretely route source audio through a submix. This is preferred for dither or other mastering processing, where you do not want unprocessed audio heard in addition to the processed signals. Use track outputs (not sends) to assign tracks to a bus path for discrete submixing. In this arrangement, the balance of processed and unprocessed signal is controlled by plug-in wet/dry settings.
The contributing track faders control the balance within the submix. The Auxiliary Input track controls the output levels of all tracks routed to it.
You can apply mix automation to the volume, pan, mute, and send level, send pan, and send mute controls of the Auxiliary Input.
You can also bounce a submix to disk to free up the voices for use by other tracks. See
Mixdown for more information.