Gál was (and remains to this day) probably better known through his activities as scholar and writer than through his music. Over the years he wrote a number of books, which brought him wide recognition and success. What characterises all of them, and constitutes one of their most appealing and valuable features, is that they stem from his own life-long concern with the music of the great composers and a deep knowledge of their works, but also from the personal perspective of his own inner knowledge of the secrets of the creative process. As a result, his writings are not simply presentations of the 'facts' or the outward circumstances of his subject, but go beneath the surface, often in an unconventional way.

His first post-war book, The Golden Age of Vienna (1948), can perhaps be seen as a homage to his homeland - it is dedicated 'To my Austrian Friends all over the World'. It is a popular rather than a scholarly work, but it characteristically sets the account of music and musicians in Vienna from Gluck to Schubert in a broad historical and cultural context, and offers insightful and original ideas on the life and works of the composers themselves.

In the early 1960s Gál wrote monographs on Brahms (1961) and Wagner (1963). These are not dry scholarly tomes - Gál hated the 'dust-swallowing' activity of library research - but spring from intimate knowledge of the composers works. As a friend and close collaborator of Mandyczewski, and co-editor of the complete edition of Brahms's works, he had a deep affinity with Brahms, enabling him to penetrate into both works and personality. With Wagner, he attempted to steer a middle way between the greatness of his music and the monstrosity of his ideology. The great value of both works is that they are written from the perspective of the practising musician rather than the mere scholar. In the 1970s Gál wrote two more monographs: on Schubert (1970) and Verdi (1975). A deep love of Schubert's music permeates the former work, while in the latter Gál's own experiences as a successful opera composer no doubt contribute to his understanding of the dramatic and literary, as well as the musical aspects of Verdi's work.

In addition to these monographs, Gál also published The Musician's World: Great Composers in their Letters (1965), a further collection of the letters of Brahms (1979), and a guide to the orchestra works of Schumann (1979).