Acoustica User Forums

Confusing tempo adjustment % question

I have a track that is 120 bpm

I select the track and go to the sound tab
I want to make it faster
i can't do that by choosing something more than 100%, it goes slower

I choose 80% and it is now faster
It's now at 150 bpm

Isn't this a bit confusing for people?

Logically (in my brain anyways)
You would think if you are adjusting a 120 bpm tempo by 80% it would now be 96 bpm
120 x .8 = 96

To get 150 bpm it would be 125% of 120 bpm
120 x 1.25 = 150

Just asking because I was trying to figure out what the new tempo was on a track and I had to go use a beat counter to figure it out after picking 80% and speeding it up

So if you want to calculate a new tempo before making any adjustments, what is the new tempo formula?

120 bpm original tempo then choosing 80% rate adjustment = what?

The percentage refers to the clip size. The clip is what you refer to as 'track' (to avoid confusion). If your clip is 4 bars and you time stretch it by 50%, the clip's size becomes 2 bars.

You can instead click "use project tempo" and then you can alter the bpm directly.

If your clip is 4 bars and you time stretch it by 50%, the clip's size becomes 2 bars.

I am talking logically, how the brain perceives the info

If you stretch something by 50% it becomes longer
4 x 1.50 = 6

If you shrink something by 50% it become smaller
4 x .5 = 2

Sorry, yes I meant sound clip, not all the sounds on a track
I am adjusting the tempo of clip/sound on a track, not all the clips on that track

The percentage refers to the clip size

Since the rate adjustment % says rate and not length, that explanation does not make sense logically

EL34 wrote:If you stretch something by 50% it becomes longer

Stretching is just a word that refers to the process of time stretching, which can go either way. If you have it refer strictly to the meaning it has in the dictionary, sure, it doesn't make sense anymore. (Although, the possibility to use 50% as well as 150% should give a clear indication that the strict meaning might not really apply. )

Since the rate adjustment % says rate and not length, that explanation does not make sense logically

Well, since time stretching is all about length (or duration), you may have to adjust your ideas about logic in this case. The rate is simply determined by a division and it can be given as a fraction, or as a percentage.

time stretch rate in % = (new length/old length)*100

Where length can be measured in various units, such as bars.

So changing the rate must mean that at least one of the things on the other side of the equation changes accordingly, so either the length of the old clip, either the length of the new clip. The old clip's length is already given, so it must be the new clip that's adjusted in length.

Hey thanks for your input

Let me ask Greg or someone at acoustica

Scenario:
120 bpm clip on a track and I want the clip to at 150 bpm
What do I choose on the drop down menu in my screen shot?

I know that it is 80% in the menu, but why?
It seems like I should be choosing 125%

Lets say I sit someone down in front of M7 and tell them this

This clip plays at 60 bpm, but I want it to go 120 bpm

Then I tell them to pick a % from the drop down menu

That's easy they say, and they pick 200%

Then I tell them that is wrong and they are confused by this

Simple logic dictates that the % on the drop down menu should match the actual speed calculation

EL34 wrote:This clip plays at 60 bpm, but I want it to go 120 bpm

Then I tell them to pick a % from the drop down menu

It's totally possible to do it this way, but indeed confusing. Time stretching is about the duration, and bpm is about the tempo. Different concepts.

So your example refers to the tempo, you want it to play twice as fast. But a time stretch refers to the idea of "i want this loop to last shorter/longer". Imagine that you hear how a clip plays until the 3rd bar, but you want it to play until the 4th bar. Having to do this by setting the bpm would be a similar nightmare.

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Edit: not sure of what i write below. In my first test this went as i expected: adjusting from 60 bpm to 120 bpm did the same thing as time stretching a clip from 100% to 50%. It made the clip play twice as fast/in half the time.
But maybe i made a mistake: if i now raise bpm, the clip becomes larger. I'm curious to what Greg/Acoustica says, or anyone else?

??-->Adjusting the tempo as you describe would require the use of the "use master tempo" button for that clip, and then setting the required bpm (in the same area you now use to select the percentage for time stretching).