Based on this, you want a multi-purpose library, and not just a graphics library. OpenGL is purely a graphics library, so doesn't handle sound and input.
I just wanted to note that OpenGL and SFML work nicely together however(or glfw, if you want another option), and the sound/input parts of SFML are rather easy to implement(same goes for glfw). So, I'd say to not let this deter you too much from OpenGL. Between the three you really have most of the basics covered I think. If you are looking for a cross-platform and open source library, I still think OpenGL is a pretty viable option for you.