tandem vs trio

tandem

noun
  • A group of two or more people, machines etc. working together; close collaboration. 

  • A method of language learning based on mutual exchange, where ideally each learner is a native speaker in the language the other person wants to learn. 

  • A bicycle or tricycle in which two people sit one behind the other, both able to pedal but only the person in front able to steer. 

  • A carriage pulled by two or more draught animals (generally draught horses) harnessed one behind the other, both providing the pulling power but only the animal in front able to steer. 

adv
  • One behind the other. 

adj
  • Together; working as one. 

trio

noun
  • A group of three people or things. 

  • A piece of music written for three musicians. 

  • A group of three musicians. 

  • Any cocktail made with a spirit, a liqueur, and a creamy ingredient. 

  • A passage in the middle of a minuet, frequently in a different key. 

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