When editing audio or recording music by taking input sound from musical instruments, it is required to route sound from one sound device to another. To perform these functions, normally a paid software suite is used, however, one can also use a number of free tools in conjunction to overcome this problem. Playthrough is an open source and portable application which routes an incoming audio stream to the output of another soundcard. Usually you can only enable playback on the same soundcard, however, Playthrough can help you route playback sound to another sound card, which can be further used with the help of audio recording software to capture audio streams.
Using Playthrough is quite simple. Select a source sound card and an output device and click Start to route audio streams from the source sound card to the output sound card or sound device. You can also use the sliders to control the volume of the input and output sound devices.
Playthrough is a brilliant little tool that works on Windows XP, Windows Vista and Windows 7.