Together with Wilhelm Friedrich Wieprecht, the director of the royal military music corps, Moritz was successful in greatly improving the valve system used on early brass instruments. These valves designed by Moritz and Wieprecht were known as “Berliner Pumpen”, and were more reliable than the previous models. Shortly after that, Moritz invented the "Bass tuba in F", the first modern tuba, which he patented in 1835. Wieprecht included the new tuba in military bands almost immediately, where its descendants remain used as the bass instrument in marching bands today. The oldest remaining original tuba from Johann Gottfried Moritz's workshop is today held in the Musikinstrumenten-Museum Berlin.
