Removing bkgnd music from bkgnd music plus vocals

Hi Experts,
I have recorded an amateur musical, with a single microphone next to the stage, picking up vocals and background “karaoke" music played from a CD (besides general noises, coughs, rumbles and all sort of fun stuff).

What I am trying to do is to get a vocal-only (plus fun stuff, I know) track by “subtracting” the CD tracks from the stage recording.
I have a track with the stage recording and another one with the songs played during the peformance.
I tried creating a stereo track with the stage recording in one side and the CD music in the other and using the Subtract mode in Stereo flip to remove the background music, but actually the background music was still there, almost as before. I have aligned the CD music to the stage recording as well as I could.

I guess it would also be possible to do some type of cancellation by moving the CD music by some milliseconds, but I wouldn’t even know where to start.

Do you think it is possible to get that Vocal-only track or shall I just give up?

Thanks in advance

Aloha V,

IMHO Never give up.

Shot in the dark here:

Did you try reversing the ‘phase’ of the CD Music while playing the track with music and vox in phase?
If the timing is ‘on’ there may be signifigant cancelation of the original music leaving the vox (and fun stuff)
to stand out.

Good Luck!

I’ve done similar before and it works pretty well. Create two tracks - one for the stage recording and the other just the instrumental track (mono would be best, but not required). Align them as close as possible by ear so you don’t hear a delay on the instruments. Then find a section where there is an instrumental section with no vocal and also a loud-ish percussion sound (if one exists). What you want to find is a section that has a waveform that is visually distinctive. Then in the project window set the height of both tracks large so you can easily see the waves on each track. Zoom way in and visually align the waves by moving one track until the percussive elements match up. Now phase reverse the instrumental track. You’ll probably hear a drop in the instruments. Select the instrumental wave object and jot down where its start position is shown on the info line. Using the info line change the start position earlier and later moving by the smallest amount possible. What you want to do is find the spot where the instruments are the most canceled out - this can be tedious and take awhile (or not if lucky). As you move closer to this perfect alignment spot the instrument volume will decrease until you reach it and then as you move beyond it the volume will start to increase again. Next move the fader on the instrument track up and down until the instruments are most canceled out. If this fader is too low you won’t cancel some of the instruments on the stage recording, and if it is too high you you’ll hear it instead of the instruments on the stage recording. Since the stage recording will include the reflected sounds of all the instruments as they bounced around the theater you will always have some residual sounds, but you should be able to vastly reduce them. You might also find that using some EQ at this point, both on the individual tracks and the mix, also improves things. Take notes as you go so if things get messed up you can return to your last-best-settings.

Great ‘specific’ tips r,

Thanks Curteye and Raino,
I am furiously trying the reverse phase plus track alignment plus balancing track volume routine, but with little success so far.
I think the problem is that the alignment is not right. There aren’t really sharp transients in the stage track I can use. There are in the CD track, but they get blurred with the background noise in what I recorded.

I works great cancelling out CD and CD phase reversed though :slight_smile: Even a one or two millisecond shift in one the tracks breaks the magic. Getting that level of accuracy in my alignment is going to be very difficult, but I’ll keep trying.

Thanks again for your help!


If in the stage recording the multiple reflected sounds dominate over the direct sound it will limit how much phase cancellation you can achieve. In that case it’s quite possible you won’t be able to do what you want without specialized tools and skills.

Why are you trying to get a recording of only the vocals? Perhaps there’s another way to get to your end goal.

Basically to do some touches to the tuning of some singers here and there (using Melodyne, btw).

I’m not Melodyne savvy but don’t they have version that deals with polyphonic pitch correction. Maybe you could use a trial copy or find someone who has that version and will help you out. While it’s not what they generally do, a good mastering studio should have both the tools and the chops for the task - plus they could clean up some of your background noises.

In the future you might consider renting some wireless mics for your principle singers to record to individual tracks.

good luck

I’ve used Melodyne poly to correct a lead vocal in a live recording, it works very well although you can hear the degradation if you go too far, or listen very carefully… Perfectly acceptable for a quicky online vid upload. When I first used it to adjust a picked guitar pattern (the guitarist had gone!) it was available on a time-limited demo, and I purchased it just after that because it worked so well.


Thanks Mike,
actually I have been playing around with the demo version of Melodyne Polyphonic and, while not perfect, it is true that I was able to improve some the major tuning problems.

Still, the idea of the reverse phase cancellation was so atractive… I will probably still give it a try every now and then :slight_smile: