Sections - Tips & Tricks

85 - Time Stretch Percentage Equations        

From: krev
Email: thefluff@fcmail.com
Date: 04-Apr-99

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 1SemitoneUP106% 2SemitonesUP112% 3SemitonesUP119% 4SemitonesUP126% 5SemitonesUP133% 6SemitonesUP141% 7SemitonesUP150% 8SemitonesUP159% 9SemitonesUP168% 10SemitonesUP178% 11SemitonesUP188% 12SemitonesUP200% 1SemitoneDOWN94% 2SemitonesDOWN89% 3SemitonesDOWN84% 4SemitonesDOWN79% 5SemitonesDOWN75% 6SemitonesDOWN71% 7SemitonesDOWN67% 8SemitonesDOWN63% 9SemitonesDOWN60% 10SemitonesDOWN56% 11SemitonesDOWN53% 12SemitonesDOWN50% 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 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: Please consult your owners manual for specific usage of percentage figures.

How to Timestretch a Sample Once you've reached the TIME page in Edit Sample, select the stretch zone -- the portion of the sample that you wish to stretch or shrink. There are basically two ways of timestretching a sample: Cyclic and Intelligent. As a rule of thumb, Cyclic works best with rhythmic samples, and Intell. with vocal or ambient/ non-rhythmic instrumental samples. Cyclic mode works by applying an algorithm for each cycle. What this means is that it analyses the samples at intervals specified in the Cycle Length field for the entire length of that sample. The cycle length can be automatically selected using the AutC button, or alternatively, one can calculate the best cycle, e.g. if you've got a four bar loop that's 16000 samples long, a 2000 sample cycle length will apply the algorithm twice for each bar. Intell. mode is a little more complicated. Instead of looking at the sample at regular specified intervals, it will look at the whole thing, and set its algorithm according to the values set out in the Qual. and Width fields. [ Reference Section Contents ]

Munchkinisation This term refers to the odd side effects that occur when transposing a sound too far away from the pitch it was originally sampled on. The human voice is a good example of munchkinisation. If you think of a tape recorder, you will understand the problem. When you play a recording of your voice back at the speed at which it was recorded, it sounds fine. Use some varispeed or play it back at twice the speed and the voice suddenly starts sounding squeaky. This is because there are characteristics in the voice's tone that cannot be transposed and give rise to this effect. Cartoon character voices were often done this way and the voice over actor's dialogue recording would be played back at a higher speed to give that cutesy, squeaky character. Munchkinisation will occur on most sounds to a greater or lesser degree. Those that are badly affected are the human voice, saxophone, piano, oboe and many others. Flutes, on the other hand, are not so badly affected, neither are many synth sounds. The way to overcome the effect is to use a technique known as multi-sampling. Here, you take samples of the instrument at different pitches (e.g. one sample per octave) and you map them out across the keyboard so that the sample never transposes too far away from its original pitch. This won't eliminate the effect but it will reduce it and the more samples you make of an instrument, the less the effect will occur. The ultimate multisample would be a different sample for every single semitone on the keyboard!