Im not sure if I am on the good section but I consider USB recording interface like a Guitar accessoirie/toy like it was saying in the forum description ... Hope one of you guys have the answer to my question !!!

I am using Tascam US-600 with cubase LE 5

I have 2 issues :

First I dont understand how to hear the midi track thought my Tascam US-600 with the mono guitar track .

Second when I Export Mix I only hear the Mono track.

Basicly it looks like the midi track is not considered by my tascam US-600 because when I click PLAY the guitar is playing thought my phone pluged into my Tascam and the Midi is playing thought my computer speakers .

I tried to change these (see image under) option but I didnt fixed the problem .

Sounds like you've set the output device wrong so that the audio is being routed to the Tascam unit instead of the pc. I'm not a windows man but I'd probably be looking at your ASIO config first or maybe even your windows general sound config. Check what your output devices are set to.
Gilchrist custom
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Hmmm ... Anyone know exactly how to fix that ? I cant get it done ...