Both 楽 (ガク) and 譜 (フ) use their On'yomi. らくふ incorrectly uses the "enjoy" reading of 楽. がくぶ misreads 譜. It refers to the written notation of music, including notes, rhythms, and other performance instructions, also known as sheet music.

楽 (ガク) も譜 (フ) も音読みです。「らくふ」は楽を「たのしい」の「ラク」と誤読。「がくぶ」は譜を誤読。楽曲を記号化したもので、演奏に必要な情報が書かれたものを指します。