1. downmix - Noun
2. downmix - Verb
downmix (third-person singular simple present downmixes, present participle downmixing, simple past and past participle downmixed)
English Wikipedia has an article on:DownmixingWikipedia
(transitive) To mix (a number of distinct audio channels) to produce a lower number of channels.
downmix (plural downmixes)
The mixing of a number of distinct audio channels to produce a lower number of channels.