G5567 ψάλλω (psállō)

KJV renderings: make melody, sing (psalms)
Strong's definition: compare G5597 (ψώχω)); to twitch or twang, i.e. to play on a stringed instrument (celebrate the divine worship with music and accompanying odes)
Derivation: probably strengthened from (to rub or touch the surface;

From James Strong's public-domain dictionaries (G), JSON edition by OpenScriptures (CC-BY-SA). Every dotted-underline word in the text links here.