What is "part-singing"

Usage examples of "part-singing".

It had cost Adam a great deal of trouble and work in overhours to know what he knew over and above the secrets of his handicraft, and that acquaintance with mechanics and figures, and the nature of the materials he worked with, which was made easy to him by inborn inherited faculty--to get the mastery of his pen, and write a plain hand, to spell without any other mistakes than must in fairness be attributed to the unreasonable character of orthography rather than to any deficiency in the speller, and, moreover, to learn his musical notes and part-singing.