Lexical Definition

‎ψάλλω‎ psállō (psal'-lo) to sing praise ^G:V
probably strengthened from (to rub or touch the surface

make melody, sing (psalms).

• compare ‎ψώχω‎)
• to twitch or twang, i.e. to play on a stringed instrument (celebrate the divine worship with music and accompanying odes)

Abbott-Smith

ψάλλω [in LXX chiefly for זמר pi. (Jg 5:3, Ps 7:17*, al.), also for נגן pi. (I Ki 16:16ff., al.) ;]
1. to pull, twitch, twang (as a bowstring, etc.; Æsch., Eur., al.), hence,
2. absol.,
(a) to play a stringed instrument with the fingers (Hdt., Plat., al.);
(b) later, to sing to a harp, sing psalms (LXX); in NT, to sing a hymn, sing praise: Ja 5:13; c. dat. pers., Ro 15:9 (LXX), Eph 5:19; dat. instr., I Co 14:15.†

Abbott-Smith References

Liddell-Scott-Jones

ψάλλω,

future ψᾰλῶ [LXX+NT]: aorist ἔψηλα [LXX+5th c.BC+]:—pluck, pull, twitch, ψ. ἔθειραν pluck the hair, [Refs 4th c.BC+] twang them, [Refs 5th c.BC+]; ἐκ κέραος ψ. βέλος send a shaft twanging from the bow, [Refs]; so μιλτοχαρὴς σχοῖνος ψαλλομένη a carpenter's red line, which is twitched and then suddenly let go, so as to leave a mark, [Refs 5th c.BC+]

__II mostly of the strings of musical instruments, play a stringed instrument with the fingers, and not with the plectron, ψῆλαι καὶ κρούειν τῷ πλήκτρῳ [Refs 5th c.BC+] [same place], et ibi [Refs 4th c.BC+]; opposed to κιθαρίζω, [Refs 5th c.BC+]; πρὶν μέν σ᾽ ἑπτάτονον ψάλλον (i.e. τὴν λύραν) Ion Eleg.3.3: absolutely, [Refs 5th c.BC+] —Prov., ῥᾷον ἤ τις ἂν χορδὴν ψήλειε 'as easy as falling off a log', [Refs 2nd c.AD+]
__II.2 later, sing to a harp, [LXX+NT]; τῷ πνεύματι [NT]
__II.3 passive, of the instrument, to be struck or played, ψαλλομένη χορδή [Refs 4th c.BC+]; also of persons, to be played to on the harp, [Refs 3rd c.BC+]

_{LSJ Scripture Refs: LXX.Judg.5.3 ☩ 1Cor.14.15 ☩ LXX.Ps.9.12* ☩ LXX.Ps.7.18* ☩ Eph.5.19}