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Production Music is designed to be used as theme or incidental music in audio visual productions such as film, television, radio and new media. The music is made widely available to professionals working in production and post production.

Because it is pre-recorded, potential users have the opportunity to test a wide range of music against picture prior to making any payment. Fees are only due when the audio visual production is exhibited, broadcast or offered for sale.
The music is not copyright free. 

People who have lived in the UK and USA during 1960s and 1970s have at some point experienced Library Music. The signature tunes for news, incidental music during sports, radio and cinema commercials and tv serials; all at some point used library music. 
One of the production music giants in those days was KPM. Their productions are better known as KPM library music productions. What was created in those studios back in those days is sheer indulgence of the highest kind. Genius musicians like Keith Mansfield, Dave Gold and Alan Hawkshaw just to name a few, were the men with Godly musical talents. 
Today, we can relish on those great KPM classics with immense ease through YouTube. Music afficionados keep posting great library music classics for everyone's pleasure. Check out a paradigm right here.