MTS-ETP: micro-tuning support for synths.

It's some additional callbacks for supporting micro-tuning in synths
https://github.com/ODDSound/MTS-ESP

Need to implement the callbacks in the client, along with the implementation of said callbacks.

Start by reviewing the MTS-ESP specification linked in the issue and locating the client callback entry points. Implement the requested micro-tuning callbacks and their corresponding behavior in the client, then verify that the callbacks work as required by the specification.

Written by the indexing model from the issue text.