MidiSynth is a simple software MIDI keyboard using Haiku's built-in synthesizer or any connected MIDI In or Out device. It can be played with the mouse and/or the computer's keyboard, and also has an interface (In and Out) to MIDI hardware and any apps that use MidiKit2.
You can choose the SoundFont to use, or disable the Haiku synthesizer altogether when you connect to some other Midi Out device.
MidiSynth supports chords, which are defined in a file and can be enabled by selecting a chord from a the Chords menu. You can even remap the keys on your keyboard.