Promos are normally sent directly to broadcasters, such as music radio and television stations, and to tastemakers, such as DJs, music journalists, and critics, in advance of the release of commercial editions, in the hope that airplay, reviews, and other forms of exposure will result and stimulate the public's interest in the commercial release.
[3] Because promos are produced in smaller quantity than releases made available to the general public, they are sometimes considered valuable collectors' items.
The promo single is usually recognized by its limited liner notes and cover artwork as well as its unique catalog number (or the occasional lack thereof).
Unlike a finished promo single, these are commonly test pressings or white labels and thus are manufactured in limited runs.
[citation needed] On rare occasions a special type of demonstration record known as an acetate disc has been distributed to radio stations as a promo.
Another type of rare item which has occasionally been used as a promo is a "test pressing" or white label record.
It is not unusual for a promo single to have no commercially available counterpart particularly in those genres that are predominantly oriented to nightclub applications.
Versions in the compilation are usually either radio edits or extended / 12" remixes of the song, depending a bit on the targeted audience.
This has the added benefit of having the songs when they are already had some airtime and are thus not the bleeding edge no-one has heard from, but still have usually not been released to the mass markets yet.
Since the advent of broad-bandwidth Internet access and professional tools such as iPool or Haulix, the online promotional distribution of music has been established.