Track priority and voice assignment are dependent on your Pro Tools hardware and software configuration.
Pro Tools|HD and HDX provide a certain number of voices (simultaneous channels of audio playback and recording), depending on the number of cards in the system. For example, a Pro Tools|HD 1 system can provide up to 96 voices of audio playback and recording, at 44.1 or 48 kHz. For details on Pro Tools system capabilities, see
Playback, Recording, and Voice Limits with Pro Tools HD.
Pro Tools systems let you play or record up to 96 simultaneous stereo or mono tracks. For details on system capabilities, see
Pro Tools Capabilities with Different Hardware Configurations.