a cappella vs music

a cappella

noun
  • A vocal performance with no instrumental accompaniment. 

adj
  • Singing solely or mainly without instrumental accompaniment. 

  • Related to a form of purely vocal music mostly associated with American college performance groups. 

adv
  • In a manner of a choir with no instrumental accompaniment; literally, "in the style of the (Sistine) Chapel (in Rome)", such as a musical Mass done a cappella. 

music

noun
  • Any pleasing or interesting sounds. 

  • A series of sounds organized in time, usually employing some combination of melody, harmony, tempo, rhythm etc. usually to convey a mood. 

  • An art form, created by organizing of pitch, rhythm, and sounds made using musical instruments and sometimes singing. 

  • Electronic signal jamming. 

  • A guide to playing or singing a particular tune; sheet music. 

verb
  • To seduce or entice with music. 

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