Having three strings: said of musical instruments: as, a three-stringed viol.
The Century Dictionary (Public Domain)
Use "three-stringed" in a sentence
"Played on the eponymous three-stringed, pear-shaped instrument (it looks like a small violin, but is held upright on the knee and bowed horizontally) and accompanied by verses of rhyming couplets (or mantinades) that are "rapped", Crete's musical legacy has a rough quality – not unlike tsikoudia, the local firewater that's served at lyra gigs."
"Started by phin three-stringed, pear-shaped lute player and rickshaw driver Noppadol Duangporn, he wanted to revive the music of his native Isan."
"The Monsters of Shamisen rock, even though they're playing a traditional Japanese instrument, a three-stringed lute that's plucked with a plectrum that looks like an windshield scraper."