Who helped to develop the role of the tuba as a solo instrument?

The aim of this thesis is to find out the process carried out by many people to achieve a solo role for the tuba. It also explains which individuals people helped the development of the instrument so as how different composers have contributed to the music field and especially to the evolution and growth of the tuba in the last century. In the musical part, the thesis talks about different standard tuba pieces and their importance.