Vocal solos, or "a cappellas," of your favourite songs can be created through a technique called phase cancellation. Electrovoice.com refers to phase cancellation as "a phenomenon where a direct radio signal and a reflected radio signal combine in the receiver." At that point, the signals cancel each other completely, creating an audio space referred to as a "dropout." Through digital audio software plug-ins, you can digitally replicate this phenomenon.
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Things you need
- MP3 or .wav files of full song and Instrumental version from the same source
- Digital recording software
- Phase inverter plug-in
- EQ plug-in
Purchase and install digital recording software. Removing background music does not require high-end studio software; a copy of Sony ACID Pro sells new for £194 and Pro Tools LE systems range from £195 to £585. You may, however, have to pay for additional plug-in packages if a phase inverter is not included within the software. Basic equalisation plug-ins are generally inclusive, but if you require a more advanced EQ device, you can find a plug-in bundle that features both.
Open the digital recording software and create a new file. Import both your full song and the instrumental version into the project, making sure that the music lines up perfectly on them. The program should automatically place both files at the beginning of the recording session. However, the music in both song files will probably not begin at the same spot, so you must drag them into alignment. Getting the two files lined up as close as possible is crucial; listen closely and zoom in on the track to make sure the wave forms match up perfectly.
Apply the phase inverter plug-in to the instrumental track and play both tracks simultaneously. If they are properly lined up, you should be able to hear only the vocals. If you're still hearing the background music, you'll need to zoom in closer on your audio files to make sure they are better aligned with each other so that the music matches on each track.
A few leftover cymbals or sound effects may be left over in the vocal track. If this doesn't bother you, feel free to leave it alone. However, if you must remove them for any reason, use the EQ plug-in to roll off any frequencies that these remnants may be sitting on. Practice makes perfect here: After you've worked with this feature enough to become familiar with it, you'll be able to eliminate noise without sacrificing the quality of the vocal lines.
Tips and warnings
- If your audio files come from different sources, they may be of different qualities or may be mastered at different volumes or frequencies. The inversion of duplicate sound waves makes this work, so the music in both audio files must be sonically identical.
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