# I NEED MATHS! How do I slow this track down to -800%?September 13, 2010 8:07 PM   Subscribe

How do I reduce something by -800% when I'm working with a scale between -99% and 99%?

I saw this and i wanted to see if I'd get roughly the same result with similar songs. I tried slowing down John Mayer's "Waiting on the World to Change" in Audacity but it will only allow me to slow something down by 99 or -99% at a time. If only I had taken math class more seriously could I figure this out! So I how do I get this John Mayer track down to the -800% it deserves to be heard at? Thanks!
posted by tunestunes to Science & Nature (15 answers total)

It won't let you slow it down more than 99% because you can't slow something more than 100%. This 800% business is maddening. If something goes at 4 beats per second, 800% of that is 32 beats per second. You cannot go 32 beats per second slower (-28 beats per second). You'd basically be playing it backwards and fast.

If you want to go at one eighth the speed, set it to 12.5%.
posted by If only I had a penguin... at 8:12 PM on September 13, 2010 [3 favorites]

12.5%
posted by radiosilents at 8:13 PM on September 13, 2010

alternately, 87.5% slower
posted by radiosilents at 8:13 PM on September 13, 2010

You cannot do this in audacity.
That Bieber song was done using Paulstretch. Just get that and type in 800%.

Using "normal" audio programs will not give you the same results as this.
posted by Threeway Handshake at 8:14 PM on September 13, 2010 [1 favorite]

So there are two keys here:

"slow down" (as opposed to "speed up")

and

800%

So let's play some word games. If you want to speed something up by 800%, that's easy, right? It's (speed * 800%) or (speed * 8), right? If you want to speed something up by 8%, well, that's easy too. It's (speed * 8%) or (speed * 0.08). Got it? Okay.

Now, slowing things down is the opposite, or more specifically the inverse, of speeding things up. I choose that word because it has a precise mathematical meaning in addition to the common-sense one. If I want to slow something down by 800%, that's the equivalent of speeding it up by a fraction. That is, to say a value less than 1. I mean, intuitively, that makes sense, right? Less than 100% as fast is slower than normal in the same way that less than 100% as big is smaller than normal. So to slow things down by 800% is to speed things up by ( 1 / 800% ) or ( 1 / 8 ).

In this case, you want

(speed * 1 / 800%) or (speed * 1/8) or (speed * 0.125)

Simple!
posted by TheNewWazoo at 8:31 PM on September 13, 2010 [2 favorites]

Seconding Threeway Handshake. I tried to do the same thing in Audacity with less than satisfactory results.
posted by easy, lucky, free at 8:56 PM on September 13, 2010

(speed * 1 / 800%) or (speed * 1/8) or (speed * 0.125)

Yes, but if you're using a copier or a scale command on a program, the number you enter for reduction isn't the percentage of the original size that you want the end result to be; the number you enter is the reduction ratio, which in this case is 87.5%, as noted by radiosilents.
posted by LionIndex at 9:06 PM on September 13, 2010

Oh never mind. the math works on that one.
posted by LionIndex at 9:53 PM on September 13, 2010

50% three times
posted by rhizome at 10:12 PM on September 13, 2010

If you want to speed something up by 8%, well, that's easy too. It's (speed * 8%) or (speed * 0.08).

I think you mean (speed * 108%) or (speed * 1.08).
posted by clorox at 11:44 PM on September 13, 2010

Heh.

A button, a button, my kingdom for an edit button.
posted by TheNewWazoo at 11:55 PM on September 13, 2010

thanks everyone. although helpful, going at 1/8th the speed isn't quite what i was looking for. threewayhandshake had the best solution cause it sounds like it's not even possible to do what i'm trying to accomplish with audacity. thanks for the help everyone!
posted by tunestunes at 12:53 AM on September 14, 2010

Yeah, 800% slower isn't an easy mathematical concept to grasp, since 100% slower is stopped.

They way they are doing it is taking 4 minutes of content and stretching it so it is 8 times longer, or 800% longer. (Because the original song is 4:20, and the new song is 35:00.)

But as others have mentioned, that kind of stretching requires a lot of smoothing and chorusing and anti aliasing and what not, so it isn't as simple as just slowing it down. You need a tool designed for that.

Music/physics/math: if you play an A note (which is 440hz) for one second, you have a waveform that has 440 peaks and valleys. To take that waveform and stretch it out but maintain the pitch, you have to maintain that rate of 440 peaks and valleys per second, and add some in. For a sin wave, that's easy enough. But for a musical tone, you've got to do some serious screwing around to maintain the same sound for an extended period of time.
posted by gjc at 6:10 AM on September 14, 2010

Maybe it's 1/16th? if 100% slower is half as slow, then 800% slower is 1/16th. Just like if it's 100% faster, it's twice as fast, so 800% faster is 16 times? Or is it 9 times faster? And then 1/9 slower?
posted by indigo4963 at 7:07 AM on September 14, 2010

Forget speed. You want to alter the length to 800%.
posted by Sys Rq at 2:22 PM on August 4, 2011

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