The Enrolling Of The Singers/Musicians (Nehemiah 7:44).
The singers were a special order of Levites (seen as such in Nehemiah 11:15-17; Ezra 3:10-11; but seemingly not designated as Levites here) who according to 1 Chronicles 6:31-32 had been responsible for leading the singing and musical accompaniment in Tabernacle and Temple worship. Asaph is mentioned in 1 Chronicles 6:39. It would appear that of the singers/musicians, only the sons of Asaph, i.e. members of the musical group of Asaph, returned at this stage. Thus in Ezra 3:10-11 we read that at the laying of foundations of the new Temple ‘they set --- the Levites, the sons of Asaph, with cymbals to praise YHWH, after the order of David the King of Israel' (see 1 Chronicles 15:16-22).
In Nehemiah 11:17 three singers are mentioned, Mattaniah, a ‘son of Asaph', who was the leading one to give thanksgiving in prayer, Bakbukiah, who was the second, and Abda, a ‘son of Jeduthun'. Many see this as indicating that there were by that stage three orders of singers in view of the fact that in 2 Chronicles 5:12 in the time of Solomon the three orders of musicians were stated to be Asaph, Heman and Jeduthun. This would make Bakbukiah a ‘son of Heman', although in 1 Chronicles 9:15 his ancestry is ignored, as here. So as with the later twenty fours orders of priests this may well have been an artificial arrangement. In Israel/Judah adoption was a common form of descent (indeed a large proportion of Israel and Judah were only children of Abraham by adoption).
‘The Singers:'
Possibly more accurately we must see them as the musicians, for part of their privilege was to play the cymbals and other instruments (1 Chronicles 15:16).
‘The sons of Asaph, one hundred and forty eight.'
Ezra 2 gives us one hundred and twenty eight. The increase occurring in the time between the two lists may be due to comings of age, or to further singers returning with the sons of Azgad (see on Nehemiah 7:17).
It would appears that of the three orders in the time of Solomon (2 Chronicles 5:12) only ‘sons of Asaph' had returned at this stage. It is, of course, always possible that of the musicians only sons of Asaph had been exiled. In Ezra 3:10-11 the lead in singing and playing was taken by Mattaniah, a ‘son of Asaph'. In Nehemiah 11:22-23 we learn of ‘the sons of Asaph, the singers, over the house of God', and they were seen as so important that ‘the king' (Artaxerxes) gave commandment concerning them, and they had a settled provision as every day required. The kings of Persia took a deep interest in looking after those who played their part in the religious ritual of their subjects and their various gods. They wanted the gods on their side.