If I were to rewrite the paragraph as follows, would it help to understand the meaning of "sing song"?:
The third concert of the subscription series was given last evening,
and a large audience was in attendance.
Mr. Edward Appleton was the soloist,
and the Boston Symphony Orchestra furnished the instrumental music.
The former showed himself to be an artist of the first rank,
while the latter proved itself fully deserving of its high reputation.
The interest aroused by the series has been very gratifying to the Committee,
and it is planned to give a similar series annually hereafter.
The fourth concert will be given on Tuesday, May 10,
when an equally attractive programme will be presented.
Hope this helps
Interested in Language