Apps with 'Sound drivers' feature
Sophisticated real-time, low latency routing of audio and MIDI data between apps.
Soundflower is a Mac OS X system extension that allows applications to pass audio to other applications.
PulseAudio is a sound system for POSIX OSes, meaning that it is a proxy for your sound applications.
FixBit Driver Update Software For Smooth PC PerformanceAutomatically Identify, Download required Drivers. > It automatically Detect Uncommon Device Drivers
SoundDesk Devices are virtual connectors that you can use to route audio across apps.