Simple computer graphical user interfaces have been created to control the tonehole and register hole parameters in the STK real-time implementation. Unfortunately, existing MIDI controllers do not provide the necessary level of control. MIDI wind controllers, for example, produce only NoteOn and NoteOff messages when a key is depressed, providing no intermediate key position information. Further, any attempt to use unconventional fingerings on such controllers are impossible. Therefore, it was necessary to construct a new controller which would provide ``continuous'' and independent key position information.
The HolyController prototype was created by ``retrofitting'' an existing Yamaha WX11 wind controller. That is, the WX11 was used for breath pressure and velocity control and its key mechanism was reworked to provide a separate stream of MIDI information regarding each key position. Force sensing resistors (FSR ) by Interlink Electronics were positioned under the WX11 keys and connected to a BASIC Stamp II (BS2-IC) microprocessing unit. The MIDI stream emitted by the BS2-IC is merged with that from the WX11 using a generic MIDI merging box, and then input to the STK model. Each tonehole and register hole model parameter is controlled with a distinct MIDI ControlChange number and value, such that 128 states are possible between fully closed and fully open.