Definition of tune up in US English:

tune up

phrasal verb

  • (of a musician) adjust one's instrument to the correct or uniform pitch.

    ‘we could hear the band tuning up’
    • ‘The sudden sound of instruments tuning up broke the eye contact at last and made us both look toward the other end of the hall.’
    • ‘Musicians in Swindon are tuning up.’
    • ‘In between the dance numbers and while the musicians were tuning up and the dancers changing shoes; you could indulge in some celebrity spotting.’
    • ‘Behind them, we hear a string quartet tuning up for its requiem.’
    • ‘The backstage area at the club is filled with a discordant mix of musicians tuning up and trams for the Disneyland concourse whizzing by.’
    • ‘The band was tuning up their instruments.’
    • ‘The crowd inside the square was moving again, filling into the center of the area as the members of the mariachi tuned up their instruments.’
    • ‘Even from the opening moments, as the band tunes up its instruments, we know this movie is going to be about the music.’
    • ‘The only music to be heard was some of the brass section tuning up their instruments.’
    • ‘Already, the members of the orchestra were tuning up their instruments so it wouldn't be too long before the show started.’