Simple Arp is a bare-bones arpeggiator. It cycles through all currently pressed MIDI notes, with your choice of speed and direction.
Simple Arp outputs MIDI only, it must be connected to any synthesizer that accepts MIDI in order to work properly. In addition the clock must be running, either in Reaktor or your host program.
An instructional video can be found here:
A bug in the User Library is not allowing me to upload the instrument version, but you can rip it out of the ensemble easily enough.
Written in Reaktor 5.9