There are two main approaches here. Maintain a constant linear velocity, in which case the disc spins slower as you move outside on the disc, thus keeping the overall transfer rate constant. The second is a constant angular velocity in which the disc spins the same speed, but the transfer rate changes depending where on the disc you are located. In fact, I'd argue that the later are better for audio, as since the speed doesn't change, the mechanisms can be made to be significantly quieter. Furthermore, since data transfer speed isn't all that important in audio it's a viable solution. The later is indeed what the CEC belt driver players use and the former is what most modern CD/DVD drives use.