The process of removing vocals from a song can sometimes be accomplished by leveraging the way stereo tracks are typically recorded. This method, which involves subtracting one stereo channel from the other, is more of a hack than a professional technique, as the general sound quality will be severely deteriorated.
The General Process
- Many instruments in a song are often recorded so that they favor one side of the stereo track over the other.
- By contrast, vocals are usually recorded in mono and played equally in both channels.
- Subtracting the right channel from the left (or vice versa) removes everything that is the same in both channels, which often includes the main vocal track.
The general steps are as follows:
- For each sample in the stereo input sound, compute the difference between the left and right channels at that point in time.
- Use this result as the corresponding sample in the mono output sound.
Caveat: This is a Hack, Not a Professional Technique
- This technique isn’t always effective and can sometimes remove parts of the music other than the vocals.
- It’s more of a simple hack than a technique used by professional audio engineers.
- Professionals use more complex and reliable techniques for this purpose, often involving spectral editing, phase cancellation, and other methods.
Pseudocode
A pseudocode representation of this process could look like this:
function remove_vocals(input_sound):
output_sound = create_empty_mono_sound(input_sound.length)
for each sample in input_sound:
output_sound[sample.index] = input_sound.left_channel[sample.index] - input_sound.right_channel[sample.index]
return output_soundThis pseudocode assumes that input_sound is a stereo sound object that has separate left and right channel arrays, and that create_empty_mono_sound is a function that creates a new mono sound object of a given length.