There are two types of music license libraries that people can obtain to help with any production needs: royalty-free and needle-drop. Here are a few aspects of each so you can choose which one better fits your needs.
The term royalty free music often brings up a sense of confusion. Some people believe that it means there is no cost to use the music. Others believe that the music is "copyright free.” However, each music library license varies to a certain extent. Generally speaking, royalty free music means that you can purchase a "lifetime synchronization license" for a particular song or collection of songs. In other words, you will have the right to coordinate the music with any production for an unlimited number of times without any additional cost.
Needle-drop music is available by individual tracks. You are charged based on the use the music, along with different licensing rates for broadcast/non-broadcast, local/nationwide and profit/non-profit. A needle-drop license is good only for a specific project, so you do not have unlimited access to the music unless you purchase a new license. However, if you want to use the music a number of times within the same production you are simply charged for a multiple drop license. Needle-drops can run from $100 - $1,500 per track depending on the licensing you choose. Also, most needle-drop libraries offer a blanket license if you prefer multiple uses of the library. Although this license gives you the rights to unlimited use of the music library, be prepared to pay more fees.
Intern, Propulsion Media Labs
Mass Communication, La Salle University