The black Yamaha MX88 is an 88-key music synthesizer with GHS weighted action that combines more than 1000 MOTIF XS sounds, class-compliant USB Audio/MIDI connectivity, along with DAW control features and iOS integration. The sounds include instruments like acoustic piano, electric piano, strings, drums, as well as complex eight-element synthesizer sounds. Each voice can be customized and stored, including the onboard VCM (Virtual Circuit Modeling) effects, which are designed to simulate the effects found on vintage keyboards. A performance mode allows for combining voices on the keyboard using dedicated Split and Layer buttons, handy for creating performances that simulate a whole band playing.

In addition to the tone generator and performance mode, the keyboard is a capable USB Audio and MIDI Interface. Connect a USB cable to a computer and monitor all the sounds from a DAW via the headphone output, or connect to external studio monitors. The audio interface is bidirectional which allows for recording the internal sounds of the keyboard directly to the computer. Connect an additional controller to the computer via the MIDI-in port, or use the keyboard to control other MIDI devices, such as hardware sequencers and groove boxes via the MIDI-out port.

Beyond the USB audio/MIDI port, the keyboard also has a USB to Device port for connecting USB devices for storing internal data to external memory. WAV files can also be played back directly from a USB stick using this port. An auxiliary stereo mini jack is available for playing back audio from external audio devices like iPods. Additionally, the synthesizer features knobs and buttons for controlling internal sounds, DAW parameters, and VST instruments.