From the Director's notes by Nick Pegg.
The Krarg voices in the completed version of Shada were electronically treated in post-production to give the creatures their gravelly tones. However, the actors who played the Krargs were still required to growl and roar in the studio to provide the raw material for these effects.
At the end of one of the recording days, our two Krarg actors were joined in the studio by other cast members and various production staff from BBCi and Big Finish. Once everyone was grouped around the microphones, I directed them through the various different Krarg effects that we required: some low growling, some enraged roaring, the 'Universal Mind' chant from the end of part five, and so on.
In the extras, you'll hear a couple of glimpses of the raw, untreated Krarg voices in the studio.
At the beginning of this clip, you can hear me cueing actor Stuart Crossman, who provides the first couple of seconds' worth of growling, followed by each of the other Krargs, one by one, as I pointed to each person in turn.
So you must bear in mind that not all of the people you can hear in this clip are actors, and not all of their Krargs proved suitable for use in post-production - especially not the last one, which is provided by a very sporting BBCi producer who shall remain nameless!