A Levite – son of Berachiah, descendant of Merari. He was also a seer (prophet), singer and skilled musician in the time of David.
1 Chronicles 15:17 So the Levites appointed Heman the son of Joel; and of his brethren, Asaph the son of Berechiah; and of the sons of Merari their brethren, Ethan the son of Kushaiah;
1 Chronicles 15:19 So the singers, Heman, Asaph, and Ethan, were appointed to sound with cymbals of brass;
1 Chronicles 16:5 Asaph the chief, and next to him Zechariah, Jeiel, and Shemiramoth, and Jehiel, and Mattithiah, and Eliab, and Benaiah, and Obededom: and Jeiel with psalteries and with harps; but Asaph made a sound with cymbals;
1 Chronicles 16:7 Then on that day David delivered first this psalm to thank the LORD into the hand of Asaph and his brethren.
1 Chronicles 16:37 So he left there before the ark of the covenant of the LORD Asaph and his brethren, to minister before the ark continually, as every day’s work required:
Psalms 50 and 73-83 inclusive are attributed to him. He is mentioned along with David as skilled in music, and a "seer":
2 Chronicles 29:30 Moreover Hezekiah the king and the princes commanded the Levites to sing praise unto the LORD with the words of David, and of Asaph the seer. And they sang praises with gladness, and they bowed their heads and worshipped.
The ‘sons of Asaph’ are mentioned in:
1 Chronicles 25:1 Moreover David and the captains of the host separated to the service of the sons of Asaph, and of Heman, and of Jeduthun, who should prophesy with harps, with psalteries, and with cymbals: and the number of the workmen according to their service was: 2 Of the sons of Asaph; Zaccur, and Joseph, and Nethaniah, and Asarelah, the sons of Asaph under the hands of Asaph, which prophesied according to the order of the king.
2 Chronicles 20:14 Then upon Jahaziel the son of Zechariah, the son of Benaiah, the son of Jeiel, the son of Mattaniah, a Levite of the sons of Asaph, came the Spirit of the LORD in the midst of the congregation;
Ezra 2:41 The singers: the children of Asaph, an hundred twenty and eight.
I hope you find this helpful.