Most analog monosynths generate a control voltage and gate signal from their own keyboard, route those signals through switches built into the CV/gate jacks on the back of the instrument and then into the synthesizer voice of VCOs and envelope generators.  The Synhouse MIDIJACK is a small computer that generates analog control signals and has input wires and output wires that route the local keyboard signals through an internal computer-controlled analog switching matrix.  When installed in the correct manner which puts the MIDIJACK "downstream" of the existing analog interface jacks,  the user may choose between MIDI control or normal use of the keyboard and CV/gate jacks.  To install,   the user simply disconnects one wire from each of the existing CV and gate jacks and solders two of the easy color-coded MIDIJACK wires to those jack terminals,  and solders the disconnected wires to two more wires on the MIDIJACK wiring harness,  then solders two MIDIJACK wires to the synthesizers' own power supply to provide power for the MIDIJACK.  When MIDI is activated by pressing the button,  the analog keyboard is automatically disconnected by the MIDIJACK computer and the analog synthesizer can be controlled from MIDI computer sequencers,  keyboards,  or any other MIDI controller.  When MIDI is turned off,  the MIDIJACK automatically removes itself from the signal path and the instrument is returned to normal keyboard and CV/gate operation.