A promotional recording, or promo (recently known as a radio single), is a recording issued on vinyl, CD, cassette tape, VHS, or DVD and distributed free in order to promote a commercial recording. Promos are usually sent out to music radio and television stations. In the UK promo recordings are also sent out to music journalists and reviewers in advance of the official release date so that their reviews will appear in the current publications. They are often distributed in plain white packaging, without the text or artwork that appears on the commercial version. Typically a promo is marked with some variation of the following text: "Licensed for promotional use only. Sale is prohibited." It may also state: "Item is to be returned to the distributor upon demand."

Before the advent of formats other than vinyl records, a type of promo surfaced known as an "acetate". These records were made of a cheaper and lower quality acetate vinyl. They were generally made in excrutiatingly low quantity and often had hand-written labels. Frequently they were only a test pressing, and thus were called "promo acetate test pressings". In modern usage the term "acetate" or "promo acetate" usually refers to a cheaply manufactured CD-R made up to efficiently promote the product with minimal expense.

Promos are distributed to expose a new product or release to those who are in a position to market it and entice the general public to purchase it. They are technically loaned to the people they are sent to, though it is implied that the loan is indefinite. In very rare cases promotional items are, in fact, recalled by the distributor. For example a promotional CD and cassette of the 1994 album Under the Pink, by Tori Amos, was recalled because Amos had not approved of the cover artwork. It was sent back with the cover art removed.

Because promos are produced in smaller quantity than releases made available to the general public, they are considered valuable collector's items. As such it is a dilemma for collectors who want to obtain them: it is illegal to sell them as they are technically still owned by the distributor, but when they are sold, they often sell for considerably more than a commonplace version of the same item. Further referencing the above mentioned Tori Amos promo: copies of it sell for hundreds of dollars as opposed to a commercially released copy which sells for ten.