Learn who owns the copyright. Check a page of sheet music for the song, and look for the copyright symbol with a name after it. This is the owner. If you can't find it, check for the name of the publisher marked anywhere on the music, and contact the publisher for the copyright owner's name. If you can't find that, search databases (see Resources).
Print and fill out the "Request for Permission to Arrange" form from the Music Publishers Association (see Resources). This form is a standard agreement for arrangement permission, and you will simply have to fill in the blanks with your name, the copyright owner's name and the name of the music.
Mail the completed form to the publisher or copyright owner. If you're unsure of the address, call the publisher ahead of time to ask.
Wait to receive the signed form back from the copyright owner. This can take any length of time, depending on how busy a composer or publisher is at the time. Sometimes, the agreement will be based upon a fee to be paid to the copyright owner. Pay this fee if necessary.
Compose your arrangement. Adhere to the terms of the contract with the copyright owner.