Demos of new songs can be given to producers before a band goes into the studio. The songwriter in a band may give rough demos of new songs to other band members. If a band or artist is looking for an agent or manager, the demo is a key tool to raise interest. And sometimes, a record label will allow the media to hear demo recordings to build some buzz around an upcoming release.
When this does happen, usually only a select few media members will get to hear the demos, and generally, this happens when demos contain "finished" songs. In other words, songs that are still in the writing and tweaking stage don't often get played for people outside the band and label.
A promotional recording, or promo, or plug copy, is an audio or video recording distributed free, usually in order to promote a recording that is or soon will be commercially available. ... Promos are often distributed in plain packaging, without the text or artwork that appears on the commercial version.
Some Promo's 7 Demo's can be very hard to locate as most will have fallen by the wayside and detroyed. Some collectors are only collecting such items and veer away from the original recording, if released that is. Some are never released and these are the ones that can fetch good money.