a cappella vs solo

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. 

solo

noun
  • A piece of music for one performer. 

  • A job or performance done by one person alone. 

  • A card game similar to whist in which each player plays against the others in turn without a partner 

  • A single shot of espresso. 

  • An instance of soloing the football. 

adv
  • Alone, without a companion. 

verb
  • To perform something in the absence of anyone else. 

  • To drop the ball and then toe-kick it upward into the hands. 

  • To perform a solo. 

adj
  • Of, or relating to, a musical solo. 

  • Without a companion or instructor. 

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