Hi Groba. Thanks for these hints. They helped! My PowerBook G4, Mac OS 9.2.2, MotU MTP AV/USB interface and Sounddiver 3.0.52 now seem to be working OK together. For the reference of anyone else who may have similar problems, here's what has to be done. (See my previous posts for a full description of my setup.) 1. Make a configuration in MacOS X Audio MIDI Setup that does NOT include the MTP/AV USB. This is to free up the interface and USB bus for use by OS 9. 2. Install OMS 2.3.8. I found the installer by a google search. It will install itself in the OS 9 System Folder. 3. Install MotU FreeMIDI 1.48. This version is available as a download at the MotU website. It too installs in the OS 9 Folder automatically. It is important to install FreeMIDI *after* OMS. Otherwise the FreeMIDI installer will not install the MotU USB and interface drivers in the OMS Folder located in the OS 9 System Folder. (There was a tech note at the MotU website that pointed this out.) 4. Run OMS Setup. Just as Groba said, the USB port did not appear alongside the modem and printer serial ports as options in the setup process; nevertheless, the MTP/AV USB was recognized when the automatic scan is performed. 5. In SoundDiver 3, choose OMS in the MIDI Communications Preferences. In my case, my main problem was that I already had FreeMIDI installed on my system when I installed OMS. Thus the necessary MotU drivers were missing from the OMS folder until I reinstalled FreeMIDI. One curiosity: I now get an error message relating to the OS X MTP driver every time OS X starts up. I am not worried about it now but I may have to sort it out later. The error says: "! System extension cannot be used. The system extension '/System/Library/Extensions/Motu MIDI Driver.kext' was installed improperly and cannot be used. Please try reinstalling it, or contact the product's vendor for an update." I'm not sure if this is a symptom of OS 9 and OS X fighting over access to the MTP, or whether the driver became corrupted when, at one point when I was monkeying around with the setup, Audio MIDI setup crashed in OS X. In any case, SoundDiver now has a new lease on life in my little studio. Thanks to those who offered advice! cheers, Eric --- In sounddiver-users@yahoogroups.com, "Urs Grossenbacher" <ursgrossenbacher@...> wrote: > > I'm not familiar with the MotU USB MIDI Interfaces. But with my Unitor8 MkII I need to install a > special Unitor8 USB driver for MacOS9 in the system extension folder and a Unitor8 OMS > driver in the system/OMS folder to get the interface recogniced. > When there is no special OMS driver available for your interface you need the "Standard > Interface OMS driver" in your system/OMS folder. > Make sure other USB drivers and system extensions in MacOS9 like "HID Library", > "InputSprocket Classic", "InputSprocket Extension" and "USB Device Extension" are enabled. > When I did my new set-up in MacOS9 the USB port wasn't shown - only the printer and > modem port. When I let OMS search for new devices it found my Unitor8 flawlessly on the > USB port. > Make sure you've got the preference pane "OMS preferred device" enabled. Chose your MotU > interface there. > Open for a change your system profiler in MacOS9 - does it show other USB devices you've > got connected. When not - we need a deeper look into your system extension...