Today we see a lot of recording dublets with (stereo) or (mono), etc. in the disambiguation comment. In order to avoid redundant and inconsistent information for work, place & location, date, involved persons, etc, the number of audio channels should not be stored on recording level but on track level. 

On the tracklist tab there should be an option to choose by medium 'number of audio channels' from a dropdown list (mono, stereo, quadrophonic, 5.1, etc. and most important: mixed). In the case of 'mixed', number of audio channels needs to be entered on track level. This is crucial e.g. for enhanced Audio DVDs which carry different formats of one recording.