TriggerTune is designed to play a melodic sequence with just the press of a (MIDI mappable) button or by an incoming MIDI note.
This allows e.g. drummers to map the ‘STEP’ button to a MIDI trigger pad and rhythmically play a pre-arranged sequence with any synth, sampler or MIDI instrument. More info.
This is a free download. Simply add a "0" into the price field. Unless you would like to donate something which is always appreciated.