clef vs curly bracket

clef

noun
  • A symbol found on a musical staff that indicates the pitches represented by the lines and the spaces on the staff 

curly bracket

noun
  • Either of the two characters { and }, i.e., left curly bracket { and right curly bracket }, with the shape of a curved, pointed line, having various uses in math, music, computer programming and chemistry. 

How often have the words clef and curly bracket occurred in a corpus of books? (source: Google Ngram Viewer )