Mulab acts here as a host for the 4 VSti racks.(a soundmodule with a device file to make)
In the composer there a 2 midichannels, but it seems that i can only send midi to one rack in Mulab (the 2 midichannels for the composer are not connected with rack 1 and 2 at the same time)
As i understand a Midi loopbackport has 16 midichannels, but Mulab allows only one midichannel(rack) ?
Strange..

