# Help with Vari-Speed recording !!!

let’s say i have a track that i change the speed of to slow it down using the “Change Speed” function.
i record another track to the slowed-down track.
how in the world do i get these two tracks back to their original speed ???
if i slowed the first track by -25%, increasing the speed by 25% doesn’t restore the speed back to original.
solving this issue would be a godsend for me & would solve so many other problems.
thanks !

You would need to increase the speed by 33.333333… percent.

It’s easier to understand the maths if you look at the “speed multiplier” setting,
A -25% speed change is equivalent to a speed multiplier of 0.75. That is, 1000 Hz becomes 750 Hz, and 100 bpm becomes 75 bpm, and in the general case:

``````new_speed = 0.75 x original_speed
``````

to change that back from “new_speed” to “original_speed”, you need to divide by 0.75.
Obviously, 0.75 = 3/4, and dividing by 3/4 is the same as multiplying by 4/3.

So the “multiplier” required to reverse the effect of “0.75 x original_speed” is 4/3 = 1.333333333…

However, the easiest and most accurate way is:

1. Make a note of the length of the original track before you slow the track down.
2. Now you can restore the original speed by using the Change Speed effect to shrink the track back to the original length.

that is so helpful !!!
i never thought about paying attention to the length of the track, so thank you so much !!!

You would need to increase the speed by 33.333333… percent.

Another trick is to simply remember the original length. Then just type that number in for the “to” Length Audacity will do the math for you.