Music signs are symbols used in musical notation to indicate the pitch, rhythm, and tempo of a piece of music. The four music signs mentioned in the crossword solutions are CLEF (4 letters), segno (5 letters), REST (4 letters), and REPEAT (6 letters). A CLEF is a symbol placed at the beginning of a staff line that indicates the pitch of the notes written on that line. A segno is a sign used to indicate the beginning of a section of music that is to be repeated. A REST is a symbol used to indicate a period of silence in a piece of music. Finally, a REPEAT sign is a symbol used to indicate that a section of music should be repeated.