It turns out that the lead singer in many bands is the only vocalist on a stereo microphone. This means that background vocals and instruments typically appear on either the left or right channel with a time delay to the other. You can exploit this phenomenon and create a karaoke machine by subtracting the left and right channels. This essentially removes any signals which are identical between the left and the right audio channel, removing the lead vocalist.
Using this LabVIEW VI:
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When the VI is running you can switch between the Left audio channel and the result of subtracting the right from the left channels. In much of the music I own, the lead singer is either significantly muffled or completely attenuated.
This VI uses the DAQ Assistant read to acquire the left and right audio channels. The result is then broken out into a Waveform Datatype using two Convert From DDT express VIs. The user may select which signal to hear. The signal is then repeated on both channels so that both speakers play the same output signal. A scalar is applied for volume control. The result is then played out the DAQ Assistant2 VI and the spectrum is graphed using the Spectral Measurements VI and a Waveform Graph.