Not unusually for a tenor specialising in Wagner roles, René Kollo did not start out singing the type of music he's best known for. Rather more unusually, he started his career as a pop singer. He eventually moved into opera instead, however, with roles such as Tamino and Lensky. Then, although he doesn't have a particularly heavy voice, he started to take on Wagner, and ended up becoming the leading Tannhäuser, Siegfried and Tristan of the late seventies and early eighties.

The results are variable. Kollo's voice is not especially beautiful, and as time went on he was afflicted more and more with a beat on his high notes. On the other hand, he is dramatically satisfying, and can often do things with a role that other tenors can't. His best recording is probably Siegfried under Marek Janowski, where his voice sounds particularly fresh and he comes nearer than most to sounding young. Beside that he gives a varied and detailed interpretation of the role, making it one of the best recordings of Siegfried around (at least for the first two acts). Evidence of his variability comes in the recording of götterdäerung which completes the Janowski cycle, however. Although it was recorded at roughly the same time, the voice sounds much more monochromatic and forced.