I present MelodyMorph, a reconfigurable musical instrument designed with a focus on melodic improvisation. It is designed for a touch-screen interface, and allows the user to create "bells" which can be tapped to play a note, and dragged around on a pannable and zoomable canvas. Colors, textures and shapes of the bells represent pitch and timbre properties. "Recorder bells" can store and play back performances. Users can construct instruments that are modifiable as they play, and build up complex melodies hierarchically from simple parts.