Locate the owner of the rights to a piece of music you want to use. Copyrights sometimes change hands, so make certain that you have the correct entity. U.S. copyright law states that for works that date from 1922 or after, you must obtain permission to use copyrighted materials. Any work before this date is in the public domain in the U.S., but it may be subject to an international copyright restriction.
Determine on the type of license you want. The license purchase price varies, depending on whether you want to use a piece of music for a one-time use or for multiple uses, such as in a nationwide commercial that will air over three months.
Contact the owner of the license to determine the cost of the type of license you want. If you have unlimited resources this might not be a factor in your decision to license a piece of music; however, if you have a tight budget, the cost of licensing the work may be an important variable in your considerations.
Sign a licensing agreement, such as a "Master Use License" for a broadcast commercial, that details the specifics of your agreement.