Audio commentary

An audio commentary is an additional audio track included on DVD and Blu-ray releases, featuring cast, crew, and occasionally fans, watching and commenting on a film or TV programme. It is selected for in the menu and plays in-sync with the video material.

The majority of Doctor Who-related releases have featured them.

New Series
For the first four years of the revival the complete series box sets included audio commentaries on every episode. But beginning in 2010, box sets only included commentaries on select episodes, with fewer and fewer episodes getting one year on year.

Torchwood
Initially Torchwood followed the same format as the New Series releases, with commentaries on every episode. However this stopped after the first series box set and wouldn't return. The second and third series box sets didn't feature any commentaries, and the fourth series only two.