The Windows USB MIDI drivers unfortunately are buggy when it comes to large sysex messages like the Blofeld uses. Also, the Blofeld USB MIDI interfaces will be shown as «USB Audio Device» unless you use the driver provided by Waldorf in their download archive. To work around the bug in the USB MIDI driver, you need to install both MIDI-Yoke and MIDItrix V1.24 and do some changes to your SD/sequencer setup. You need to be aware that MIDI-Yoke provides something like a virtual MIDI cable (please read the documentation), so no application should ever attempt to open both the input and the output part of a MIDI-Yoke interface, because that would create a MIDI loop. Most sequencers grab all interfaces they can get hold of, consult the fine manual on how to prevent that. In SD under Windows you do this in the [SoundDiver] section of WIN.INI (see the example below). You should set up the SD so that it opens one set of MIDI-Yoke interfaces only as MIDI Inputs and the rest of the MIDI-Yoke interfaces only as MIDI Outputs and leave all USB MIDI interfaces without their own driverdisabled (INI parameter is set to 0). This will ensure that SD only sees the MIDI Yoke interfaces and never tries to open both ends of the same MIDI Yoke «cable». Then connect the MIDI Yoke Inputs and Outputs with the real (USB) MIDI interfaces via MIDItrix (MIDI Yoke 1 → Waldorf Blofeld, Waldorf Blofeld → MIDI Yoke 2). On the connections to the USB MIDI interface (Waldorf Blofeld, both input and output), enable the "defragment" option. This will collect all parts of a SysEx message and send it from a single large buffer to the USB MIDI driver. If you plan to use SoundDiver for Windows with the Blofeld that is the only way it is going to work reliably when you only use USB and not an additional "normal" MIDI interface to send to the Blofeld.
