The period in Mainz was for Gál highly stimulating and varied. Not only was he active in the conservatory, but he was, with Ernst Toch and Alban Berg, on the directorate of the Allgemeiner Deutscher Musikverein (the German Music Society). This was a respected organisation which organised regular Festivals of Contemporary Music, each time in a different town. Every submitted work was assessed by a jury of two, who had to write a detailed report. Berg and Gál were responsible for the Austrian section, and it is remarkable, and a testimony to the integrity of both, that despite their radically different conceptions of music, they almost always agreed on their assessment of the originality and musical competence of the works.

Gál enjoyed these occasions, as they gave him contact with directors of conservatories and university professors from all over Germany. He always came back with a store of amusing anecdotes from the world of German music. Hanna accompanied him on some of these trips, though they usually only attended the concerts themselves when a piece by Hans was on the programme. This was the case in Krefeld, where his Epigrams received their first performance, in Königsberg, for his Ballet Suite for Orchestra (Op. 36), and finally in Zürich, in 1932, for a performance of his second String Quartet.

Meanwhile, the flow of his own compositions in no way abated. Here belong, apart from the above-mentioned Ballet Suite, the fairy-tale play Der Zauberspiegel ('The Magic Mirror', Op.38), which had its first performance as a Christmas play in the Breslau Theatre in 1930, the Serenade for violin, viola and cello (Op.41), written in 1932, the Violin Concerto (Op.39), also written in 1932 and first performed in Dresden in February 1933 by Kulenkamp, Fritz Busch conducting, and above all a new opera Die Beiden Klaas ('Rich Claus, Poor Claus', Op.42), whose fate will concern us below. He was now generally recognised and widely regarded as one of the most respected composers of his generation.

The Gáls returned to Austria for their summer holidays, or occasionally to Switzerland. For shorter breaks they went into the nearby Rheingau and Taunus forests. They also spent some time at a children's home in the Black Forest - a contact that they were soon to be grateful for.