Now, all the tracks will sound via my boss gt-100 and my guitar amp Wait, i connect my boss gt-100 via usb ,it own its asio driver So you either need to split in the analog realm before you get to the computer, or use an audio interface with multiple independent outputs to achieve the split. The basic problem is that you want two different signals, one for your amp, and one for the speakers, and your GT-100 doesn't have multiple independent outputs, and you can't solve this by using your computers built in outputs as a second send. Or, if your audio interface has multiple outputs, you can run from the GT-100 into reaper, and then send just the guitar input track back out to the amp, and assign the backing tracks to another output that goes to your speakers.

The the amp gets the guitar sound, the audio interface records the guitar sound, and reaper sends the backing track through the outputs of your audio interface and into your speakers. Exactly what audio interface do you have?). Split the output from the GT-100 so that it goes to your amp and into your audio interface (I'm assuming that you aren't calling your GT-100 your audio interface. So if you use its output, you're going to have to choose between having that output monitored through the amp, or your speakers, or both (by splitting the signal with an analog adapter), but you can't send a different mix to both the amp and your speakers.

Your GT-100 only allows for one output mix.

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