Time-stretch Algorithm for Keygroups

Nooblet question incoming:

I am working on some multi-sampled instruments and I am able to get them sampled via the C1,C2,C3, etc. method but, over the span of the 13 semi-tones in between there is a small gap in the length of the key presses. The length gets shorter as they pitch up.
In the Z4/Z8 sampling engine, isn't there some type of stretch that is automatically applied due to the program being a keygroup? Thus, making the note all the same length but pitched accordingly?

i may be wrong, but i don't think there is automatic timestretching when you're building a keygroup. you can loop a portion of each sample (like the tail end of the sample), or the whole thing. you can time stretch in sample edit, but you will not be happy about it. i used longer samples and smaller intervals, like 3rds, or 5ths instead of every octave.

Thanks.

Now, has there ever been a device that could ever do exactly what I am trying to do easily? I don't think such a hardware sampler exists.

Maybe this should be on the feature request list for the Ren.

(pages JAHrome)

Mike Boogie wrote:Now, has there ever been a device that could ever do exactly what I am trying to do easily? I don't think such a hardware sampler exists.

The Roland VP-9000 could do it.

When I get home I will try and recreate your issue. I never noticed what has happened to you with my Z4 but I have never thoroughly put in the samples like you have for one sound.

To piggy back on the other hardware that does this well....roland v-synth(which has variphrase in it) has the format knob and synth power. The MC909 has variphrase in it also but it is not as deep as the V-synth.

The don't remember gaps in the Yamaha a4000 when in a different pitch either. Now I need to go in the studio and play around.

peace
Ian

Standard stuff with all hardware samplers - ie notes get shorter as you travel up the keyboard range. There are a few exceptions like the Roland.

Keep in mind time stretching will can change the character of the sound quite a bit - although some think its subtle. Granular time stretching (aka Ableton for example) simply fills the gaps with nonsense and plays havoc with the transients. I always hated it, and still do.

What you experience is really a much more natural sound even though you do get the shorter notes. Think about all those early Hip Hop records - its mostly all natural pitching on the drums to get the tempo accurate - many still do it like that, my self included. Also keep in mind that those shorter synth/keyboard sampled notes can build a bit of character in to the sound - depends on the sound of course. You can of course loop the sound but again that totally depends on the sound.

If you really want to avoid the shortened note scenario your best bet is to sample every single note, or at least every second or third note. The 4k has the memory for it and it really is way better than time stretching.

The only time I will ever resort to time stretching is vocals. Even then i will do my best to avoid it. Or if I'm doing it for a creative effect. I like time stretching when its totally exaggerated

I figured as much, damn shame that this particular problem has only been rectified in only a few pieces of hardware over the years. I can't think many software solutions that could help either???

Mimik by Open Labs was similar in a way but, I think it sampled every note and velocity layer.

Whomever would be able to find a solution to this may be in for a swim in a large pile of money. Imagine being able to sample 1 NOTE and have it stretched across all 61-88 keys properly.

Shit, if the REN's time-stretching is so butter, why the hell is this not at the top of every feature request list I see??

I notice that my fantom S samples good too. You put one note in it and it puts them all up and down the keyboard well.

If you do a drum loop then it gets faster and shorter.

After reading what Labcoats said now I better understand what Mike meant. That's standard stuff.

Some yamaha items have the time stretch built in and sample your loop and make it fit the right time. THe SU700 and the a4000 do this just so you know.

Peace
ian

To be more precise, I am not working with drums or vocals. Let's say I have a horn stab sample tuned precisely to C3. Whenever I play a note lower than C3, of course the pitch will lower but the length of the note is also longer. The exact opposite happens in reverse, the sample gets shorter and shorter.

It's annoying when trying to play chords.

Making this feature could be something that may separate the men from the boys.

(Calls Akai...)

Aren't you glad I own a Akai S-2000. From the manual...

Time Stretch Percentage Equations Transposition Formula

To transpose upwards: Multiply 1.0595 by itself for as many semitones and then multiply the result by 100.
Example: For 3 semitones - 1.0595 x 1.0595 x 1.0595 x 100 = 119%

To transpose downwards: Divide 100 by 1.0595 multiplied by as many semitones as is required.
Example: For 2 semitones - 100 /(1.0595 x 1.0595) = 89%

Time Stretch Percentage - Cents Transposition Table

(Pitch Up "+")-------------------------------
1) Semitone UP 106%
2) Semitones UP 112%
3) Semitones UP 119%
4) Semitones UP 126%
5) Semitones UP 133%
6) Semitones UP 141%
7) Semitones UP 150%
Semitones UP 159%
9) Semitones UP 168%
10) Semitones UP 178%
11) Semitones UP 188%
12) Semitones UP 200%
***********************
(Pitch Down "-")---------------

1) Semitone DOWN 94%
2) Semitones DOWN 89%
3) Semitones DOWN 84%
4) Semitones DOWN 79%
5) Semitones DOWN 75%
6) Semitones DOWN 71%
7) Semitones DOWN 67%
Semitones DOWN 63%
9) Semitones DOWN 60%
10) Semitones DOWN 56%
11) Semitones DOWN 53%
12) Semitones DOWN 50%

NOTE: You will have to adjust your samples to the actual key within you keygroup and sample editing fields. It is up to you to know that actual difference of the pitch and have a good ear.
---------------------------------------------------------------------------------------------
"Time in general..."

Time Stretch/Shrink Formula
New time divided by original time x 100
Examples: To calculate percentage for stretching 5 secs to 7 secs:
7 divided by 5 x 100 = 140%

To calculate percentage for stretching 18 secs to 25.5 secs:
18 divided by 25.5 x 100 = 141.6%

To calculate percentage for shrinking 36 secs to 29 secs:
29 divided by 36 x 100 = 80.5%
Note: Minutes need to be multiplied by 60 first:
eg 2 mins, 34 secs = (2 x 60) + 34 = 154

---------------------------------------------------------------------------------------------
"For Beat Loops"

BPM Stretch/Shrink Formula
Original tempo divided by new tempo x 100
Examples: To stretch 124 BPM to 135 BPM:
124 divided by 135 x 100 = 91.85%

To shrink 112 BPM to 105 BPM:
112 divided by 105 x 100 = 106.666%

NOTE: Say if you doing this in a program like Apple's Soundtrack Pro...

if the length of the sample is 103320 , then do these steps....

1) Find out the BPM of the beat sample.

sample rate * 1000 * 60 seconds * beats of sample (i.e.4 beats to the bar)
all divided by
the length of the sample

(44.1 * 1000 * 60 * 4) / 103320 = approx. 102.44
103 bpm after round-up

2) You want it to be 95 bpm, so...
103 / 95 = 1.08421052631579

3) Now, multiply the LENGTH of the sample by the result of the "Step Two". This will give you the stretch or shrink that you desire...
103320 * 1.08421052631579 = 112020.632578947

Of course you will have to tweak the sample before you use it. This will let you keep the original pitch of the sample, too. I hope that all of this has helped! Send me a link to a pic of an MPC-4000 with a skin the color of Chartreuse Yellow (hex code DFFF00) as payment! Peace

Mad Cherokee

You sir... are a GOD amongst men!!!

Great work it been a minute to learn something new for the 4k!

madcherokee wrote:Aren't you glad I own a Akai S-2000. From the manual...

Time Stretch Percentage Equations Transposition Formula

To transpose upwards: Multiply 1.0595 by itself for as many semitones and then multiply the result by 100.
Example: For 3 semitones - 1.0595 x 1.0595 x 1.0595 x 100 = 119%

To transpose downwards: Divide 100 by 1.0595 multiplied by as many semitones as is required.
Example: For 2 semitones - 100 /(1.0595 x 1.0595) = 89%

Time Stretch Percentage - Cents Transposition Table

(Pitch Up "+")-------------------------------
1) Semitone UP 106%
2) Semitones UP 112%
3) Semitones UP 119%
4) Semitones UP 126%
5) Semitones UP 133%
6) Semitones UP 141%
7) Semitones UP 150%
Semitones UP 159%
9) Semitones UP 168%
10) Semitones UP 178%
11) Semitones UP 188%
12) Semitones UP 200%
***********************
(Pitch Down "-")---------------

1) Semitone DOWN 94%
2) Semitones DOWN 89%
3) Semitones DOWN 84%
4) Semitones DOWN 79%
5) Semitones DOWN 75%
6) Semitones DOWN 71%
7) Semitones DOWN 67%
Semitones DOWN 63%
9) Semitones DOWN 60%
10) Semitones DOWN 56%
11) Semitones DOWN 53%
12) Semitones DOWN 50%

NOTE: You will have to adjust your samples to the actual key within you keygroup and sample editing fields. It is up to you to know that actual difference of the pitch and have a good ear.
---------------------------------------------------------------------------------------------
"Time in general..."

Time Stretch/Shrink Formula
New time divided by original time x 100
Examples: To calculate percentage for stretching 5 secs to 7 secs:
7 divided by 5 x 100 = 140%

To calculate percentage for stretching 18 secs to 25.5 secs:
18 divided by 25.5 x 100 = 141.6%

To calculate percentage for shrinking 36 secs to 29 secs:
29 divided by 36 x 100 = 80.5%
Note: Minutes need to be multiplied by 60 first:
eg 2 mins, 34 secs = (2 x 60) + 34 = 154

---------------------------------------------------------------------------------------------
"For Beat Loops"

BPM Stretch/Shrink Formula
Original tempo divided by new tempo x 100
Examples: To stretch 124 BPM to 135 BPM:
124 divided by 135 x 100 = 91.85%

To shrink 112 BPM to 105 BPM:
112 divided by 105 x 100 = 106.666%

NOTE: Say if you doing this in a program like Apple's Soundtrack Pro...

if the length of the sample is 103320 , then do these steps....

1) Find out the BPM of the beat sample.

sample rate * 1000 * 60 seconds * beats of sample (i.e.4 beats to the bar)
all divided by
the length of the sample

(44.1 * 1000 * 60 * 4) / 103320 = approx. 102.44
103 bpm after round-up

2) You want it to be 95 bpm, so...
103 / 95 = 1.08421052631579

3) Now, multiply the LENGTH of the sample by the result of the "Step Two". This will give you the stretch or shrink that you desire...
103320 * 1.08421052631579 = 112020.632578947

Of course you will have to tweak the sample before you use it. This will let you keep the original pitch of the sample, too. I hope that all of this has helped! Send me a link to a pic of an MPC-4000 with a skin the color of Chartreuse Yellow (hex code DFFF00) as payment! Peace

Mad Cherokee

Great post! Thanks for sharing this, since I read this I noticed something convenient on the MPC. I'm sure the 4000 has the same thing, but I'm talking about the beat loop function on MPC2K/2KXL. I guess it's supposed to tell you the BPM of a loop, kinda useless but here's how you can use this for a quick reference of time stretch %'s for semitone keygroups:

1) make a new blank/silent sample, and give it a loop length that is 600 milliseconds. (26460 samples @ 44100kHz)

2) in sample parameters screen, set the loop settings to 1 beat, it should tell you this loop is: 100.0BPM at normal tuning.

3) when you adjust the tuning in the same window the BPM will actually be the same as the correct time stretch % you would need to get a tuned sample to play for the same length as the original. it checks out.

Sticky this!

on the mpc 2500 you can make a phrase sample that will keep the sample length the same when playing it across the keyboard or sampler, works well,
just make a basic patch phrase at the tempo of project and try it on any sample, may have to tweak settings if its a complex sample