Ringtone
Ringtone means a phonorecord of a part of a musical work distributed as a Digital Phonorecord Delivery in a format to be made resident on a telecommunications device for use to announce the reception of an incoming telephone call or other communication or message or to alert the receiver to the fact that there is a communication or message.
Source
37 CFR § 385.2
Scoping language
Unless otherwise specified, capitalized terms in this part shall have the same meaning given to them in 17 U.S.C. 115. For the purposes of this part, the following definitions apply: