Can sound/music be linked to annotations?
For those of us in the scientific community, this is perhaps the most useful application of sound.
Architects, Engineers etc would find sound linked to annotations of their models useful.
Anyone trying to explain a diagram or parts of a model or structure would find this essential if dealing
in multiple languages 
A simple method of dropping a mp3 file into an annotation would assist in the preparation of CHECKLISTS
that would complement the use of augmented VR.
For example: refer to "Google Glass on the Manufacturing Floor using Proceedix"