Sample Inversion

A trick known as “sample inversion”, though not fool-proof, can help you capture just the acapella of your favorite song. Sample inversion works by canceling out all of the background frequencies in a track, inverting the audio on the instrumental track, and leaving you with the vocal frequencies to do with as you please. Sample inversion can be applied by following these steps :

Step 1. In your favorite audio editor (I like using Audacity for this), import both the instrumental and the full song on to separate audio tracks.

Step 2. Since the song you’re working with is most likely in stereo, convert both tracks to mono audio and pan one all the way left and one all the way right. Audacity will split both stereo tracks when converting to mono, so also remove any extra tracks that may have been created during this step.

Step 3. Take care to make sure that both tracks are perfectly in sync with each other, lining up the start point of each waveform. The position of the peaks and valleys in the waveform and how well they line up is crucial here. This alignment must be surgically exact in order to isolate the vocal properly.

Step 4. Once you’ve lined up the audio, select your instrumental track and use the Invert option to flip the waveform upside down. This will create the audio cancellation effect we’re going for by adding interference to the instrumental of the layered tracks, letting the vocals shine through without any background frequencies.

If you hear a muffled backing track with a clean vocal part, then pat yourself on the back because you’ve successfully applied sample inversion! If not, you shouldn’t get discouraged. This technique relies heavily on both tracks being mastered in the same exact way at the same exact tempo and at a high quality bit-rate. Getting all these elements spot on can be difficult, but try using this technique on older tunes for surprising results.