The Hagedorn Spectrum and the Dual Resonance Model: An Old Love Affair

In this contribution I recall how people working in the late 1960s on the dual resonance model came to the surprising discovery of a Hagedorn-like spectrum, and why they should not have been surprised. I will then turn to discussing the Hagedorn spectrum from a string theory viewpoint (which adds a huge degeneracy to the exponential spectrum). Finally, I will discuss how all this can be reinterpreted in the new incarnation of string theory through the properties of quantum black holes.