MIDI Keyboard is a free Android app developed by Mobileer Inc under the Multimedia category. It is intended for software developers or OEMs to test the Android MIDI feature in M. The app serves as a MIDI controller that can be used to send NoteOn/Off messages to external MIDI devices or virtual MIDI services.

One of the main features of MIDI Keyboard is its ability to play notes on external MIDI devices, laptops, or other MIDI apps. However, it is important to note that the app does not produce sound by itself and is not a synthesizer. Instead, it is a MIDI controller that can be used with a synthesizer to produce sound.

To connect the app to a laptop, users need to drag their finger down from the top of the Android screen, select the "USB for Charging" icon, choose "MIDI", and launch the MIDIKeyboard app. From there, users can select "Android USB Peripheral Port" from the "Receiver for Keys" menu at the top.

Overall, MIDI Keyboard is a useful app for software developers or OEMs looking to test the Android MIDI feature. Instructions and links to source code can be found on the official Android website.