MIDIKeys is a versatile MIDI keyboard controller designed for sending MIDI messages to synthesizer apps and hardware MIDI synthesizers. It does not generate sound independently but serves as a tool for playing VST-style MIDI synthesizers through MIDI hardware interfaces connected to the iPhone dock or virtual MIDI instruments like IK Multimedia SampleTank and ThumbJam running in the background on your iPhone.

With MIDIKeys, users can transpose the entire range up or down within a three-octave limit by interacting with the intuitive interface. The app offers options for fixed or variable note MIDI Note On event velocity based on touch position, along with the ability to send real-time volume, expression, modulation, or wind controller MIDI messages by tilting the device. Users can customize MIDI channel settings, velocity values, and controller options to suit their preferences.