The 2M is two unity gain mixers in parallel. Each mixer has level controls for the 3 inputs and also for the output.
As its design has been specially focused on audio applications, all the input potentiometers are audio-taper type while the output ones are linear.
Low distortion / high quality audio operational amplifiers have been selected in order to achieve clean audio mixing. It is also DC-coupled so it can perform CV signal mixing as well. Especially useful in small systems where submixing or stereo mixing patches are required.