I'm thinking a cheap controller paired with a small piano-only sound module, like the Alesis nanopiano, but that can power the controller over a USB cable. Does such an animal exist? Is there a better way?
Reading that again, I don't understand. Is there now a software Alesis Nanopiano? Or a new hardware one with USB? The original nanopiano did not have USB.
The MX49 has a power brick and can't be powered via USB. But it does work standalone (with headphones, since it has no built-in speakers).