Add ability to comment on voicemail transcription

Hi there, I would like to be able to add a comment or note to a voicemail transcription.  For example, when the transcription has made an error, I want to be able to add a comment or note that shows the correction, without actually editing the original transcription.  (For record-keeping reasons, it would be a terrible idea to be able to edit the original transcription, at least without some kind of tracking and version history being saved.)  Thanks.