a cappella vs sing

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. 

sing

noun
  • The act, or event, of singing songs. 

verb
  • To display fine qualities; to stand out as excellent. 

  • To be capable of being sung; to produce a certain effect by being sung. 

  • To soothe with singing. 

  • To confess under interrogation. 

  • In traditional Aboriginal culture, to direct a supernatural influence on (a person or thing), usually malign; to curse. 

  • To produce a 'song', for the purposes of defending a breeding territory or to attract a mate. 

  • To produce any type of melodious vocalisation. 

  • To produce musical or harmonious sounds with one’s voice. 

  • To express audibly by means of a harmonious vocalization. 

  • To make a small, shrill sound. 

  • To perform a vocal part in a musical composition, regardless of technique. 

  • To relate in verse; to celebrate in poetry. 

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