The first edition, a single-volume work, was produced in 1938, edited by Percy Scholes, and was written almost entirely by him alone.
The second edition, published 1939 includes a 64-page categorised List of books about music in the English language by Scholes.
Wherever possible, Scholes tried to use primary source material, rather than summarizing other people's work. His preface to the First Edition describes how he played and read through thousands of sheets of music, as well as reading thousands of concert programs and studying "old literature and long-bygone musical journals". From this research, he produced about fifty-five volumes of notes. Each of these was devoted to a separate branch of musical knowledge. He then sought peer review of each of these volumes with specialists in the particular branch of musical knowledge. Finally, these volumes were broken up and re-constituted in alphabetical order.
Scholes' intention was to produce a work relevant to a wide range of readers, from the professional musician to the concert-goer, "gramaphonist", or radio-listener. His work was aimed at a reader for whom it "will neither be beyond the scope of his pocket nor embarrass him by a manner of expression so technical as to add new puzzles to the puzzle which sent him to the book". The result was a work which was highly accessible to the general reader, as well as being useful for the specialist.
While scholarly and well-researched, Scholes' style was also sometimes quirky and opinionated. For instance, his original articles on some of the twentieth-century composers were highly dismissive, as were his articles on genres such as jazz. His entry on the can-can concluded "Its exact nature is unknown to anyone connected with this Companion."