This is in Sakka-pañha Sutta in DN 21.
Then said Sakka, the king of the gods, to Five-crest the Gandhabba—‘Difficult of approach, dear Five-crest, are Tathāgatas, to one like me, when they are rapt in the bliss of meditation, and for that purpose abiding in solitude. But if you were first to gain over the Exalted One [by your music] then might I afterwards come up and visit him, the Arahant, the Buddha supreme.’
‘So be it and good luck to you!’ consented Five-crest, and taking his lyre he went to the Indra-Sal tree-cave. On coming there he thought—‘Thus far will the Exalted One be neither too far from me nor too near to me, and he will hear my voice.’ And he stood on one side, and let his lyre be heard and recited these verses concerning the Awakened One and the Truth, the Arahants and Love...
When Five-crest had finished the Exalted One said to him—‘The sound of your strings, Five-crest, so harmonizes with that of your song, and the sound of your voice with that of the strings, that your lyre does not too much colour your song, nor your song too much colour your play. Where, Five-crest, did you learn these verses concerning the Awakened One and the Truth, the Arahants, and Love?’
Here is the Sinhalese version.