You can locate the key information on the Internet by visiting the performing rights society web sites (http://www.bmi.com, http://www.ascap.com, or http://www.socan.ca) and determining which organization controls rights for the source song. (You may also find help at the Harry Fox website at http://www.harryfox.com.)

Some detective work may be required. BMI's searchable database includes more than 20 entries, for instance, for songs titled "Yesterday." If you can't locate the song you're looking for online, try phoning the performing rights organizations and ask for the "song indexing" department. Once you have the publisher's name and address, phone or write the publisher to determine if they will grant clearance for the source music. Many publishers, unfortunately, have a policy not to grant permission for sampling.

If the publisher can't lead you to the owner of the master recording, you can check online record stores or the Phonolog directory at your local record shop to find the record company that is currently releasing the source music. Locating master owners may prove troublesome -- record companies may fold or sell their copyrights to other companies. In addition, rights in masters may revert to the original artists after a number of years. In that case, you may have to use the assistance of a clearance expert or sampling consultant.