ANd I agree that songs in films are hardly "commercial recordings," however, I am trying to gauge Bob's particular interest here. Both commercial discs and film soundtracks can be grouped as non-field recordings, i.e. performances designed for presentation, not documentation. There is something crucial in the act of presentation that involves a degree of self-consciousness and a well-formed idea of what one is trying to put across. Excuse my babbling on...I am currently working on an argument about how (so I claim) the re-conceptualizing of shanties as "folk songs" affected how people decided to present them.