When I connect my keyboard to Music Maker 2013 via MIDI, no matter what instrument I play on the keyboard the program always turns the sound into piano music. If I play a different instrument or even play with my own beats on the keyboard, how do I get music maker to record exactly what is played?
That's because MIDI does not transmit AUDIO. MIDI is a computer control language designed to control MIDI capable hardware electronic instruments and software "virtual" instruments (VSTi). You are hearing only the "acoustic piano" because it is the default VSTi in the Vita MIDI Editor in MMM. To hear a different instrument in MMM, you would have to choose a different virtual instrument in Vita.
Now...to hear and record the various voices from your keyboard, you would have to connect the AUDIO outputs on your keyboard to the Line-IN on your computer or audio interface.