Tempo Control and Warping. AUTOHELM ABLETON

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Tempo Control and Warping. AUTOHELM ABLETON | Manualzz

118

Chapter 9

Tempo Control and Warping

Unlike music stored on tape or in a traditional digital audio workstation, the music in Live remains elastic at all times. Live is capable of time-warping samples while streaming them from disk so as to synchronize them to the current Live Set's tempo. This happens without affecting the pitch, which can be changed independently. Mixing and matching audio from different origins is therefore extremely easy.

9.1

Tempo

9.1.1

Setting the Tempo

The Control Bar's Tempo eld allows you to change the playback tempo of your Live Set at any time, in real time. You can even

automate the tempo

to create smooth or sudden tempo changes along the song timeline. For maximum tempo control during performance, you can

MIDI map

separate controllers to the Tempo eld on both sides of the decimal point. Setting one knob to control coarse tempo in BPM and another to control ne tempo

The Control Bar's Tempo

Field.

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119 in hundredths of a BPM allows for enough precision to adjust to live performers or other unsynchronized sources.

You can have an external sequencer (or drum machine) play along with Live or have Live play along with the sequencer. The respective settings are made in the MIDI/Sync Preferences, and the EXT switch next to the tempo control is activated to have Live follow an external

MIDI clock source. Please refer to the section on

synchronization

for details.

9.1.2

Tapping the Tempo

You can use Live's Tap Tempo function to set the tempo at any time. As you click the Control

Bar's Tap Tempo button once every beat, the tempo of the Live Set will follow your tapping.

The Tap Button.

It is better to assign the Tap button to a computer key than using the mouse. Click on the

Control Bar's KEY switch to enter Key Map Mode; then select the Tap button; press the key you would like to use for tapping; click the KEY switch again to leave Key Map Mode. The assignment will take effect immediately. The Tap button can also be assigned to a MIDI note or controller, like a foot switch, in a

similar fashion . Although Live responds to your

tapping immediately, it does apply some degree of inertia to prevent sluggish behavior in the software. The more taps Live receives in a row, the more precisely it will be able to conclude the desired tempo.

You can also use tapping to count in: If you are working in a 4:4 signature, it takes four taps to start song playback at the tapped tempo.

The Key Map Mode

Switch.

9.1.3

Nudging the Tempo

The Nudge Buttons.

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120

Although Live can be easily

synchronized to external MIDI devices , you may nd yourself in

situations in which you need to adjust to sources that aren't locked to one tempo, such as live musicians or turntables. As long as your Set's tempo is basically the same as that of the unsynchronized material, you can use the Nudge buttons to temporarily speed up or slow down Live's playback to match what you hear. As with the Tap button, these buttons are much easier to use when

mapped to MIDI controllers .

9.2

Time-Warping Samples

Live's ability to play any sample in sync with a chosen tempo is a unique and important feature. In addition, you can warp the rhythmic ow of a piece, changing its feel, or even move notes to other meter positions.

A clip's warping properties are set in the

Sample box , which is a sub-section of the Clip View.

The most signi cant control here is the Warp switch, which toggles a clip's warping on or off. The Warp section of Live's Preferences will determine the default warp settings for new clips, but they can always be overridden here on a per-clip basis.

When the Warp switch is off, Live plays the sample at its original, normal tempo, irrespective of the current Live Set's tempo. This is useful for samples that have no inherent rhythmic structure: percussion hits, atmospheres, sound effects, spoken word and the like.

Turn the Warp switch on to play rhythmically structured samples (such as sample loops, music recordings, complete music pieces, etc.) in sync with the current song tempo.

To direct Live's assumptions about new samples, use the Record/Warp/Launch tab of Live's

The Sample Box's

Warping Controls.

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121

Preferences. If the Auto-Warp Long Samples preference is on, Live assumes that long samples contain music that should be played in sync with the Live Set's tempo. If you would rather have Live default to playing long samples as they are, disengage this preference.

9.2.1

Tempo Master/Slave

All warped clips in the Arrangement View have one further option: They can be de ned as

tempo masters by toggling their Master/Slave switches. Any number of clips can be set as tempo masters, but only one clip at a time can actually be the tempo master. This distinction is always granted to the bottom-most, currently playing clip in the Arrangement View.

The clip that is the current tempo master will play as if warping was off, but with one important difference the rest of the Live Set will be warped so that it plays in sync with the current tempo master.

This is achieved by adding tempo automation to the Master track for the duration of the tempo master clip. You will notice that the Tempo eld in Live's Control Bar becomes disabled in this state; this is because all tempo control is handed over to the tempo master clip.

When toggling a clip's Master/Slave switch, or when deleting a clip that was set as tempo master, the Master track tempo automation is removed again, restoring the proper tempo to the region. If you wish instead to keep the generated tempo automation to continue working with it, then (PC) /

Ctrl

(Mac) on the Control Bar's Tempo eld, and choose the Unslave Tempo Automation command. All clips will then be set to Slave, but the tempo automation will remain in place.

Note that when Live's

EXT switch is enabled , the Master/Slave switch has no effect and

appears disabled.

9.2.2

Warp Markers

Think of a sample as a rubber-band that you want to pin to a (musical time) ruler. In Live, the pins are called Warp Markers. A Warp Marker locks a speci c point in the sample to a speci c place in the measure. You can use any number of Warp Markers to create an arbitrary mapping of the piece's inherent rhythm to a musical meter.

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Warp Markers are set in the Clip View's Sample Display by double-clicking within the sample. They can then be dragged or moved with the arrow keys to different points in time.

Warp Markers can also be deleted by double-clicking them, or by pressing the computer keyboard's or

Delete key after selecting them.

Double-Clicking In the

Sample Creates a Warp

Marker.

When working with your sample, you can have Live scroll the Sample Display to follow playback. Use the Control Bar's Follow switch to activate this feature. It also might be helpful to vertically resize the Sample Display by dragging on the split line between the Clip

View and the Session View track area.

The Follow Switch in the

Control Bar.

Transients and Pseudo Warp Markers

When you rst load a sample into Live, Live automatically analyzes the audio and nds its

transients. These are the points in the audio where notes or events begin, and are usually good places to put Warp Markers. Transients appear as small markers at the top of the sample display after zooming in.

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123

As you mouse over transients, temporary pseudo Warp Markers appear. These have the same shape as regular Warp Markers, but they're grey. Double-clicking or dragging a pseudo Warp Marker creates an actual Warp Marker or, if there are no Warp Markers later in the clip, changes the tempo for the clip segment. Holding the

Ctrl

(PC) /

(Mac) modi er while creating a Warp Marker on a transient also creates Warp Markers at the adjacent transients. Holding the modi er while clicking on a pseudo Warp

Marker allows you to drag the transient to a new position. Once a Warp Marker has been created, holding while dragging the Warp Marker will move the waveform beneath the marker, rather than the marker itself.

You can also select a range of time and create Warp Markers at all of the transients within the range via the Create menu's Insert Warp Markers command. If there are no transients within your time selection, a Warp Marker will be created at the end of the selection.

Although Live usually does a good job of placing transients in the right places, you can delete and create transients as well, via the corresponding commands in the Create menu.

Transient Markers.

Saving Warp Markers

Your Warp Markers will automatically be saved with the Live Set, but you may also want to save them with the sample le itself, so that they are reconstructed anytime you drag the le into Live. To do this, click the Clip View's

Save button .

Note that if a sample has a

saved set of Warp Markers , Auto-Warp will have no effect. When

this is the case, you can use any of the (PC) /

Ctrl

(Mac) context menu commands described in this section to initiate auto-warping.

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9.2.3

Using Warp Markers

In the following sections, we will look at a couple of applications for time-warping samples.

Warping is, of course, an optional property of clips.

Syncing Straight Loops

When you import a sample that represents a well-cut musical loop of 1,2,4 or 8 bars in length, Live usually makes the correct assumptions to play the loop in sync with the chosen tempo. It creates two Warp Markers, one at the sample's beginning and one at the end.

The Seg. BPM eld displays Live's guess of the loop's tempo; if you happen to know the tempo of the loop, you can type it in here. Sometimes Live's guess of the original tempo is wrong by half or double. If so, correct this by clicking on the buttons labeled *2 and

:2, respectively. The sample plays at double speed when you press :2 because you are changing Live's interpretation of the sample's tempo, which serves as a point of reference for determining the required time-stretch factor.

A Two-Bar Loop as It

Appears in the Clip

View, by Default.

Syncing Uncut Loops

When importing a loop that has not been edited into a well-cut loop, Live will play it out of sync. Suppose there is a portion of silence at the sample beginning, prior to the rst beat. You can easily correct this by placing a Warp Marker at the beginning of the audio and dragging it so that it lines up with the beginning of bar one in the timeline. Likewise,

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125 you can eliminate silence after the actual loop end by placing a Warp Marker at the sample's right edge.

Syncing Odd-Length Loops

If you import a sample that contains a seven-bar loop, Live initially assumes the loop is eight bars long (or four, depending on its length) and plays it out of sync. For correct playback, the marker at the end of the sample needs to be at the beginning of bar eight, not bar nine.

To x this, simply drag the ending marker to the correct position.

If Live's initial guess had been a four-bar loop, the eighth bar may not initially be visible. In that case, you can drag the Warp Marker at the end toward the right until the eight becomes visible.

Manipulating Grooves

You can now create any number of Warp Markers by double-clicking within the sample or on transient locations. Drag in a straight looped sample, set a few Warp Markers, and move them around to see what happens. Warp Markers really serve two purposes:

1. to provide a correct interpretation of the ow of musical time in the sample;

2. to mess up the ow of time in the sample.

Setting the Warp

Markers for a Poorly Cut

Loop.

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126

If a single event in a percussion loop comes late, just pin a Warp Marker to it and drag the marker to the correct beat position. You may want to pin the adjacent events as well, to avoid affecting neighboring regions in the sample.

Removing a sample's natural groove by applying Warp Markers is an interesting creative method, particularly in conjunction with Live's

ability to impose an arti cial groove onto clips in real-time .

Using Warp Markers to

Manipulate the Groove.

Syncing Longer Pieces

Live's Auto-Warp algorithm makes longer samples and entire songs readily available for integration into your project. You can use the

Browser

to import long samples or MP3, AAC,

Ogg Vorbis, Ogg FLAC and FLAC les.

When you drag a le into Live that is too long to justify the assumption that it is a loop or a one-shot, Live will auto-warp the clip by default (though this can be changed in the

Record/Warp/Launch Preferences ).

Note that, for the auto-warp mechanism to work, les which are being imported into the program for the rst time will need to undergo a rst-time

analysis process

and will not be immediately available for playing or editing. As explained in the section in this manual on analysis les, analysis can be batch-processed with the (PC) /

Ctrl

(Mac) context menu's Analyze Audio command. Once analysis is nished, you can view the results of

Auto-Warp's assumptions about the le.

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127

Auto-Warp's Results in the Clip View.

As long as Auto-Warp made the correct set of informed guesses, the clip will be ready to play in perfect sync with the Live Set's tempo. However, if Auto-Warp does not quite do what you want, you can control its results. The remainder of this section will focus on various ways of guiding Live's auto-warping. Remember that the metronome in the Control Bar will probably come in handy as you warp longer pieces.

It might happen that Auto-Warp guesses the tempo correctly but gets the downbeat wrong.

To remedy this, you can do one of the following:

ˆ Hold the key while dragging the rst Warp Marker. This will allow you to adjust the position of the waveform under the Warp Marker.

ˆ Zoom in and create a Warp Marker on the downbeat. Then drag it to the beginning of bar 1 in the timeline;

ˆ Use the start marker's

Here command.

(PC) /

Ctrl

(Mac) context menu to select the Set 1.1.1

The Metronome Switch.

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Directing Auto-Warp is also relatively simple when you have imported a perfectly cut loop.

You can tell Auto-Warp to work accordingly using the Warp As ...-Bar Loop command. Live will propose a loop length that makes the most sense given the current Live Set's tempo.

Decreasing the Live Set's tempo can, for instance, lead Live to assume the loop is 8 bars at

90 BPM instead of 16 bars at 180 BPM.

Sometimes more accurate control of Auto-Warp is necessary. The best way to go about warping a clip that requires more detailed attention is in sections, working gradually from left to right. You can set a Warp Marker by double-clicking in the sample to the right of each correctly warped section, pinning it into place. The shortcuts for working with the

clip loop brace and start/end markers

can speed up this process considerably.

You might also nd it helpful to select multiple Warp Markers for moving by selecting them with the or

Ctrl

(PC) / (Mac) modi ers held down.

Using the Context Menu to Direct Auto-Warp.

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The four Warp From Here commands provide various ways of resetting Warp Markers to the right of the selected grid marker or Warp Marker, leaving Warp Markers to the left untouched. These commands are also available from the start marker.

ˆ Warp From Here runs the Auto-Warp algorithm on the material to the right of the selected marker.

ˆ Warp From Here (Start At ...) directs Auto-Warp to use the current Live Set's tempo as a starting point for tempo tracking. The strategy here is as follows:

1. Deactivate the Warp switch for the clip so that it plays unwarped;

2. Use the Control Bar's Tap Tempo button to tap along, thereby setting the

Live Set's tempo to match that of the clip;

3. Turn warping on again and use the Warp From Here (Start At ...) command to tell Auto-Warp to use your tapped tempo as a reference.

ˆ Warp From Here (Straight) tells Auto-Warp that this is a clip with no tempo variations

(common in electronically produced works). Auto-Warp will then set a single Warp

Marker derived from its guess of the le's original tempo.

ˆ Warp ... BPM From Here will also set a single Warp Marker, but in this case, Auto-Warp is forced to interpret the clip as exactly matching the Live Set's tempo. This is useful in cases when you happen to know the exact BPM value of an electronically-produced work and can type it into the Control Bar before warping.

Multi-Clip Warping

When clips of equal length are multi-selected, adding or changing Warp Markers for one clip will apply identical Warp Markers to all. This is convenient in any situation where several tracks have the same rhythm, and you wish to alter the timing of each recording in the same way. A common scenario would be when multi-tracking a band's performance, where the musicians all play in time with each other, yet the timing itself is in some way awed.

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9.2.4

Quantizing Audio

In the previous section, you learned how to adjust the timing of events in audio les by manually dragging Warp Markers along the timeline. But it is also possible to automatically snap the entire sample to the grid at once by using the Quantize command. To do this, click in the background of the sample editor and choose the Quantize command from the Edit menu, or use the

Ctrl

U

(PC) /

U

(Mac) hotkey. This will quantize using default settings, or the settings that you previously applied.

To adjust your quantization parameters, open the Quantization Settings dialog from the Edit menu.

Using the options presented here, you can select either the current grid size or a speci c meter value for quantization. You can also quantize without that quantized feel by adjusting the Amount control, which will move Warp Markers by a percentage of the set quantization value.

Quantizing Audio

Samples.

9.3

Adjusting for Good Stretching Quality

Live offers a number of time-stretching modes to accommodate all sorts of audio material.

Each clip's time-stretching mode and associated parameters are set in the Clip View's Sample

Box.

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The warp modes are different varieties of granular resynthesis techniques. Granular resynthesis achieves time compression and expansion by repeating and skipping over parts of the sample (the grains ). The warp modes differ in the selection of grains, as well as in the details of overlapping and crossfading between grains.

Let's investigate which warp modes work best for different types of signals and how to adjust the warping controls for clean stretching. It's also fun to misuse these controls to achieve interesting artifacts instead of accurate stretching.

9.3.1

Beats Mode

Beats Mode works best for material where rhythm is dominant (e.g., drum loops as well as most pieces of electronic dance music). The granulation process is optimized to preserve transients in the audio material.

Use the Preserve control to preserve divisions in the sample as boundaries when warping.

For the most accurate results, particularly with percussive material, choose Transients. This setting uses the positions of the analyzed (or user-created) transients to determine warping behavior. To preserve speci c beat divisions regardless of the sample's contents, choose one of the xed note values. For some interesting rhythmic artifacts, choose large note values in conjunction with pitch transposition.

The Transient Loop Mode chooser sets the looping properties for the clip's transients:

Loop Off Each segment of audio between transients plays to its end and then stops.

Any remaining time between the end of a segment and the next transient will be silent.

Loop Forward

Each segment of audio between transients plays to its end. Playback then jumps back to a zero-crossing near the middle of the segment and continues looping until the time when the next transient occurs.

Loop Back-and-Forth

Each segment of audio between transients plays to its end.

Playback then reverses until it reaches a zero-crossing near the middle of the segment, and then proceeds again towards the end of the segment. This pattern continues until the time when the next transient occurs. This mode, in conjunction with the Preserve Transients selection, can often result in very good quality at slower tempos.

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The Transient Envelope slider applies a volume fade to each segment of audio. At 100, there is no fade. At 0, each segment decays very quickly. Long envelope times can help to smooth clicks at the end of segments, while short times can be used to apply rhythmic gating effects.

9.3.2

Tones Mode

Tones Mode serves well for stretching material with a more or less clear pitch structure, such as vocals, monophonic instruments and basslines.

Grain Size provides rough control over the average grain size used. The actual grain size is determined in a signal-dependent manner. For signals with a clear sense of pitch contour, a small grain size works best. Larger grain sizes help avoid artifacts that can occur when the pitch contour is unclear, but the tradeoff can be audible repetitions.

9.3.3

Texture Mode

Texture Mode works well for sound textures with an ambiguous pitch contour (e.g., polyphonic orchestral music, noise, atmospheric pads, etc.). It also offers rich potential for manipulating all kinds of sounds in a creative way.

The Grain Size control determines the grain size used, but unlike in Tones Mode, this is a setting that Live will use unaltered, without considering the signal's characteristics.

Fluctuation introduces randomness into the process. Larger values give more randomness.

9.3.4

Re-Pitch Mode

In Re-Pitch Mode, Live doesn't really time-stretch or compress the music; instead, it adjusts the playback rate to create the desired amount of stretching. In other words, to speed up playback by a factor of 2, it's transposed up an octave. This is like the DJ stretching method of using variable-speed turntables to sync two records, or what happens to samples in samplers when they're transposed.

The Transpose and Detune controls have no effect in Re-Pitch Mode.

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133

9.3.5

Complex Mode

Complex Mode is a warping method speci cally designed to accommodate composite signals that combine the characteristics covered by other Warp Modes; it works well for warping entire songs, which usually contain beats, tones and textures.

Complex Mode is a rather CPU-intensive function, using approximately ten times the CPU resources required by the other Warp Modes. As such, you may want to

freeze tracks

where

Complex Mode is used or

record

the results as a new clip to use as a substitute.

9.3.6

Complex Pro Mode

Complex Pro Mode uses a variation of the algorithm found in Complex mode, and may offer even better results (although with an increase in CPU usage.) Like Complex Mode, Complex

Pro works especially well with polyphonic textures or whole songs.

The Formants slider adjusts the extent to which the formants of the sample are compensated when transposing. At 100%, the original formants will be preserved, which allows for large changes in transposition while maintaining the sample's original tonal quality. Note that this slider has no effect if the sample is played back untransposed.

The Envelope slider also in uences the spectral characteristics of the material. The default setting of 128 should work well for most audio. For very high-pitched samples, you may have better results with lower Envelope values. Likewise, low-pitched material may sound better with higher values.

9.3.7

REX Mode

REX Mode differs from the other Warp modes in several ways. Most notably, it is not available as an option in the Clip View's Sample Box, but is instead enabled automatically when loading a le in REX format. REX les, associated with the program ReCycle by Propellerhead

Software, contain embedded tempo and timing information and will synchronize to your Set's tempo just like any other audio le.

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Although REX les are audio les, they can quickly be transformed into playable instruments via the

Slice to New MIDI Track

command, which is available in the Create Menu or the

(PC) /

Ctrl

(Mac) context menu for the Clip.

Warp Markers/parameters,

Clip Envelopes

that affect warping properties, and the

Clip

Nudge

controls are not available for REX les.

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