strum on

strum on (something)

1. To play a stringed instrument by brushing or stroking the strings. A few of us were strumming on our guitars as we sat around the camp fire. It was such a classy wedding. They even hired someone to strum on a harp while the guests were being seated.
2. To play something, such as a chord or song, on a stringed instrument by brushing or stroking the strings. I never got past strumming a couple basic chords on the guitar. Anything more advanced than that was just too difficult for me. He loves strumming lighthearted melodies on his banjo.
See also: on, strum
Farlex Dictionary of Idioms.

strum something on something

to brush or play with the fingers some stringed instrument, such as a guitar. She strummed a nice little melody on her guitar. He strummed the accompaniment on the guitar.
See also: on, strum
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • strum
  • strum on (something)
  • air guitar
  • pull strings, to
  • stroke (one's) ego
  • stroke ego
  • scrape away at (something)
  • accompany (one) with (some instrument)
  • accompany with
  • the world's smallest violin