Hi Ricky,
Tyros4 has only ONE Custom Normal Voice Bank (MSB 63, LSB 0) and ONE Custom Drum Voice Bank (MSB 62, LSB 0).
To use Custom Voices on Tyros4, they MUST be INSTALLED (by using INDIVIDUAL LOAD or LIBRARY LOAD). When you only COPY .uvn/.uvd files to the Tyros4's hard disk (but not install these voice files), these voices can NOT be used!
BTW: On Tyros4 the installed Custom Voices can be selected in PRESET tab, but the Wave data of the Custom Voices are stored in the FLASH ROM Expansion module, when the voices are installed.
Best regards,
Chris
P.S.
User Voices of either Preset or Custom Voices (and saved to User drive or internal hard disk) can NOT be accessed via MIDI, in principle!