What does the "Invert" effect do?

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pinacoladaxb
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What does the "Invert" effect do?

Post by pinacoladaxb » Thu Nov 26, 2009 6:18 am

Haha I know this is a lame question, but Google didn't help. It should be easy to answer anyway. :) I found that you can remove the guitar track from most commercial rock music by inverting the right stereo track and then setting the left and right stereo tracks to mono. How does this work?

Bonus question: How could I do the opposite of what this does and get only the other tracks to play? ;)

kozikowski
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Re: What does the "Invert" effect do?

Post by kozikowski » Thu Nov 26, 2009 7:04 am

If you magnify the blue waves on the timeline enough times, you eventually get down to the up and down motion representing the vibration of the strings of a musical instrument or the vibration of the air when you sing.

Stereo works by presenting two waves, one for left and the other for right. Any instrument appearing on the far right in your headphones for example, only produces waves on the right track.

Anything appearing in the middle produces exactly the same waves on the left and right tracks. Invert, when applied to only one track, say 'right', reverses the up and down motion of the waves. When you add the two tracks together, the waves of whatever is in the middle cancel out. Instruments and singers not in the middle will not cancel out, since they have more waves on one side than the other.

Audacity has a pre-packaged tool called Center Pan Remover that does the whole job for you.

If you throw enough arithmetic at it, you can cancel out singers or instruments not in the middle and some software packages can leave the singer and delete everything else. That's called Vocal Isolation.

Voice Removal or Isolation
--Center Pan Remover (Voice Remover--Search the page for "Center Pan Remover")
http://audacityteam.org/download/nyquistplugins
--Voice Trap
http://www.cloneensemble.com/vt_main.htm
--Extra Boy
http://www.kvraudio.com/get/1651.html
--Kn0ck0ut
http://www.freewebs.com/st3pan0va/


This rarely works like you want it to because the list of "what could go wrong" is pretty stiff.

-- It doesn't work at all on mono shows.

-- It works very badly on highly MP3 compressed music.

-- You get a mono show at the end, not stereo music.

-- Any stereo effects, echo or reverb added to the voice will get left behind giving you "ghosts" in the music.

People usually ask about this just before they try to remove the vocal from a highly engineered and produced mono MP3 they got from the internet.

Good luck with that.

Koz

kozikowski
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Re: What does the "Invert" effect do?

Post by kozikowski » Thu Nov 26, 2009 7:13 am

Download and put this short performance in Audacity...

http://www.kozco.com/tech/LRMonoPhaset4.wav

It's my single voice only on the left, only on the right, mixed to mono, and then intentionally damaged so left and right are out of phase or inverted to each other. Magnify the blue waves of each one to see what's going on.

Drag Select a small portion and Apple-E. Do it again. And Again.

Return to the full show with Apple-F.

Koz

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Re: What does the "Invert" effect do?

Post by jimbo2010 » Fri Apr 16, 2010 5:55 pm

I use a PC not a mac, but does this invert actually do anthing? I cannot get it to work. There used to be a program called "Mirror Maker". This flipped actual music vertically so if there was alow note, you get a high note and visa versa. Does this do that? If so, what do you have to do.

There is no explanation as to how to actually get it to work. I put a radio programme into it, and inverted it - only to get the same with some clips missing - the audio kep[t jumping, and NO DIFFERENCE AT ALL in pitch, notes etc.

Can you please tell me what would I need to do what I want to do? Can anyone suggest another program if Audacity won't do it?

Thanks.
James

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Re: What does the "Invert" effect do?

Post by steve » Fri Apr 16, 2010 6:56 pm

If you zoom in really close on a waveform so that you can see the wiggly line going up and down, then apply the "Invert" effect, you will see that it does exactly what it says on the tin - it turns the sound wave upside down.

In this picture the bottom track is a copy of the top track and has then been "inverted".
tracks000.png
tracks000.png (14.79 KiB) Viewed 21985 times
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jimbo2010
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Re: What does the "Invert" effect do?

Post by jimbo2010 » Fri Apr 16, 2010 7:54 pm

In that case, why would a 2 hour radio show not chagne? Thought the music would all be diffferent. Why not? 9BTW there was speech in this as well. Thanks.

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Re: What does the "Invert" effect do?

Post by steve » Fri Apr 16, 2010 9:07 pm

Inverting a waveform does not actually make it sound different.

Imagine a vibrating string, like the string of a guitar that has been strummed -
It could be vibrating
up - down - up - down - up - down...
If we "invert" that, it will vibrate
down - up - down - up down - up...
but it will still sound like a guitar string vibrating.

Whatever that "Mirror Maker" program did, it is a completely different effect to the "Invert" effect in Audacity.
This could be the type of thing you are looking for: http://www.youtube.com/watch?v=h47AcMMwjhg
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jimbo2010
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Re: What does the "Invert" effect do?

Post by jimbo2010 » Fri Apr 16, 2010 9:45 pm

I think that is what I was after yes. Will have a look. Thanks.

As for this programme, it appears to be very good. My only problem is that where some sound is clear like FM quality, when I tried to remove a hum in the background, it went all grainy. Really odd.#

Thanks agian.

kozikowski
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Re: What does the "Invert" effect do?

Post by kozikowski » Mon Apr 19, 2010 2:54 am

<<<My only problem is that where some sound is clear like FM quality, when I tried to remove a hum in the background, it went all grainy. Really odd.#>>>

Perfect place to start a new post.

Koz

jimbo2010
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Re: What does the "Invert" effect do?

Post by jimbo2010 » Mon May 31, 2010 12:10 am

Can you please explain - I have a mono audsio track with music and a female voice-over. How do I remove the female voice over to leave just the musci?

Thanks.
James

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