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Practical Groove Quantisation In Digital Performer

Digital Performer Tips & Techniques
Published August 2005
By Andrea Pejrolo

The Track List window, Sequencer window and Waveform editor in Digital Performer, an extremely powerful combination of tools for analysing, creating and altering MIDI and audio grooves.The Track List window, Sequencer window and Waveform editor in Digital Performer, an extremely powerful combination of tools for analysing, creating and altering MIDI and audio grooves.

This month's workshop aims to help you get into the groove more effectively, through the use of DP's sophisticated quantisation facilities.

The term 'groove' has historically been related to live performance — that is, a musical situation in which the 'human factor' plays a crucial role. In more recent years, though, the term has migrated from grimy jazz clubs to the more antiseptic environment of the project studio, a transition that's been facilitated by the availability of the 'groove quantisation' feature in some of the leading MIDI + Audio sequencers on the market. While Digital Performer initially led the way, competing applications such as Logic, Pro Tools and Cubase have recently caught up by revamping their groove quantisation features and by pushing the limits once again in terms of flexibility and ease of use. The four main digital audio applications on the market all address, in one way or another, how to groove-quantise a MIDI part or an audio part (in some cases, both), but this article is going to address some aspects of how Digital Performer, in particular, goes about the job. (For more about the principles of groove applied to quantisation and an explanation of how Groove Quantisation came about, see 'The Birth of Groove Quantisation' box.)

Applying A Groove

The latest version of DP (4.52 at the time of writing) has once again established a new standard in terms of flexibility, precision, and integration between MIDI and audio groove quantisation. Before going into more detail, though, let's run through how you apply a groove to an existing MIDI region in DP. The Groove Quantisation (GQ) function can be chosen by selecting Region / Groove Quantize or by pressing Command G. The GQ window has a simplified version and a more advanced form (see screens right). You can toggle between the two versions by selecting the More/Fewer Choices button.Practical Groove Quantisation in Digital Performer

As with any quantisation action you take in DP, you must first choose the region that you want to quantise. You can do so from any editing window, or directly from the main Track List. After selecting the region you're going to quantise, select the GQ option from the Region menu. The preset grooves in DP are organised into Folders, Main Categories and Sub-categories. The Folder level is used mainly to sort your grooves in a more efficient way, and the Folders are stored in the Grooves Folder inside your MOTU DP 4.5 Folder. You can create your own Folder directly from the finder and organise your grooves according to your personal workflow.

As default choices, DP offers DNA Groove and Other Grooves. The former definitely has the more interesting and musical grooves, while in the latter you can find grooves that recreate the feel of legendary drum machines such as the Linndrum and the MPC series.

If you choose the DNA Groove folder, you're presented with a choice of four main categories: Shuffles, Straight, Pushing and Laid Back. Double-clicking on one of the main categories opens up the Sub-categories selection menu. Here you can choose from a list of options based on the same overall groove, each selection providing small variations on the same groove, giving you the highest level of flexibility. Clicking on the More Choices button allows you to select how each parameter of a groove template (timing, velocity and duration) will affect your selected region. Altering a percentage with one of the sliders on the more complex Groove Quantise page changes the balance between the original feel with which you recorded the region and the feel of the groove template you're applying (higher values translate into parts that sound closer to the groove template chosen, while lower values allow you to retain some of the original feel that you played).The simplified (left) and full-strength versions of the Groove Quantise window. The simple window allows you to choose and apply a groove and variation feel, while the more complex one (accessed via the More Choices button) also offers sliders for varying how much of the groove's note Timing, Velocity and Durations will be applied to the region you're quantising.The simplified (left) and full-strength versions of the Groove Quantise window. The simple window allows you to choose and apply a groove and variation feel, while the more complex one (accessed via the More Choices button) also offers sliders for varying how much of the groove's note Timing, Velocity and Durations will be applied to the region you're quantising.

Although it's difficult to generalise, and the way you set up these parameters can vary depending on the style and the part you're quantising, I've found that values of around 70 percent for timing and 40 percent for velocity are a good starting point, especially for rhythmic parts such as drums and percussion. You can use the Preview button to temporarily apply the selected groove settings to the current region. Once you're satisfied, click the Apply button.

Create Your Own!

Groove quantisation is particularly appealing because it enables the composer to create or extrapolate, his/her own grooves from MIDI and audio parts. While the ability to create a groove template from a MIDI part has been available for a long time in DP, the ability to do the same from an audio part came as a new addition with version 4.5.

Creating a groove template from a MIDI part is fairly simple:

  • Select the MIDI region from which you want to extrapolate the groove (a two-bar or four-bar selection usually works very well).
  • Now select Region / Create Groove.
  • In the Create Groove window select New File, in order to create a new main groove category (for example, Swing Grooves).
  • Open the category just created, by double-clicking on its name, and use the 'New Groove Name' field to assign a name to the new groove (see the screen overleaf). Click OK.
  • From now on, the groove just created will be available from the GQ window.

While this technique allows you to expand your groove library, in reality it represents only a small improvement over the bundled presets. Custom groove quantisation gets really interesting when audio material is used as the source for grooves. The technique involves, first, the analysis of a soundbite containing the groove, then the extrapolation of the groove itself, and is particularly useful not only because it allows you to expand your groove library, but also because it can be used as an analytical tool for studying the details of a particular groove or live performance. Let's first take a look at how we can create our own grooves from audio material.

The Birth of Groove Quantisation

The original concept of groove quantisation and how it might be applied to a MIDI performance was developed by acoustic researcher Ernest Cholakis in the mid- and late 1990s. In his studies, Cholakis analysed the recordings of professional studio musicians (mostly drummers and percussionists) in order to be able to describe, in a rational and objective way, the essence of their grooves. The map on which these groove descriptions are based uses three main parameters: timing, velocity and duration. By altering slightly the relationships between each of these parameters over time, a musician is capable of building a groovy performance that is peculiar to his or her own playing style. Cholakis was able to 'can' the grooves of several musicians and extract their styles using mathematical algorithms. The grooves created are called DNA grooves and they can be bought from the Canadian company Numerical Sound (www.numericalsound.com). Basic DNA grooves have been bundled, with Performer first and with Digital Performer later, for many years. These basic bundled grooves include such general categories as Pushing, Laid Back, Straight and Shuffle, but keep in mind that, for each of these categories, you have the option of choosing from several additional variations, such as the one shown in the screens above.

Engineering The Groove

The Create Groove window is where you can save the feel of a selected MIDI part as a new groove template.The Create Groove window is where you can save the feel of a selected MIDI part as a new groove template. DP 4.52 has a very sophisticated engine under the hood that enables you to analyse a soundbite in terms of tempo and hit-points — or 'beats', as DP calls them (a beat usually corresponds to a specific transient of the waveform that is being analysed). This terminology might sound familiar if you've used applications such as Recycle from Propellerheads. Once DP is 'aware' of the beats (transients) present in a soundbite, you can, for example, quantise the audio without having to slice the soundbite into separate parts, or easily adjust the tempo of the soundbite to the tempo of the sequence (and vice-versa), and, of course, create a new series of grooves based on the positions of the detected beats. I find the last capability the most groundbreaking and fascinating of them all. Can you imagine being able to extrapolate Peter Erskine's swing groove, or the famous hi-hat swing pattern played by Jimmy Johnson of the Duke Ellington Band? That's exactly what we'll do in the following examples. In addition, wouldn't it be great if we could compare the grooves from these two famous drummers and analyse how they interpreted the concept of swing? We'll do that, too, so read on!

The first step we need to take in identifying the beats inside a soundbite is to find the soundbite's tempo. This is a procedure that's probably familiar to many DP users, as it was introduced in earlier versions of the software. Although the operation is not strictly necessary in order to identify the beats inside a soundbite, it will definitely increase the accuracy of your final identification, so I recommend including it in your to-do list. To find the tempo of a soundbite:Setting Soundbite tempo is the first step recommended in the process of placing beat markers inside a soundbite. In this window you can tell DP the length of your selected soundbite, in beats and ticks. The example shows a soundbite of two bars in 4/4, or eight beats. DP calculates the soundbite's tempo using this information.Setting Soundbite tempo is the first step recommended in the process of placing beat markers inside a soundbite. In this window you can tell DP the length of your selected soundbite, in beats and ticks. The example shows a soundbite of two bars in 4/4, or eight beats. DP calculates the soundbite's tempo using this information.

  • Select an exact number of bars (trim the soundbite so that it is exactly two, four or eight bars in length).
  • Select the soundbite, then choose Audio / Soundbite Tempo / Set Soundbite Tempo.
  • In the Set Soundbite Tempo window (see screen top right), input the Length according to how many beats and ticks you selected (for example, if you selected a two-bar loop in 4/4, input 8/000).
  • DP will automatically show the tempo of the soundbite in the lower-right corner of the Set Soundbite Tempo window, and it will stamp it into the header of the audio file so that this particular soundbite will carry the tempo information across multiple DP projects.
  • Once DP is aware of the soundbite's tempo, you can move on and start identifying the beats. First, select the soundbite.
  • Open the Waveform Editor by selecting Audio / Edit in Waveform Editor. If you're a seasoned DP user you probably know that you can do several things in the Waveform Editor, most of them based on destructive editing. In order to analyse the transients of the soundbite and identify its beats, select the Beats tab at the top of the Waveform Editor window (see screen below).

You should now see a series of vertical blue bars running across the selected soundbite. These lines identify the transients/beats that DP automatically detected. The green handle linked to each beat represents the relative velocity/volume of each beat. To change that, simply click and drag up or down with the mouse on the corresponding handle. (Keep in mind that this won't alter the actual volume of the transient in the waveform.) You can quickly adjust the threshold used by DP to identify the beats by selecting Adjust Beat Sensitivity from the Beats menu in the top area of the window. The Adjust Beat Sensitivity slider (see top screen, opposite) can be used to fine-tune DP 's beat-detection engine for the selected range of the soundbite.

In the Waveform editor, open the same soundbite whose tempo you've just set and choose the Beats tab at the top of the window. The vertical blue lines you now see are the 'beats' (transients or places of rhythmic stress in the music) that DP has identified automatically. They can be moved manually if necessary, by dragging on the green 'handle'.In the Waveform editor, open the same soundbite whose tempo you've just set and choose the Beats tab at the top of the window. The vertical blue lines you now see are the 'beats' (transients or places of rhythmic stress in the music) that DP has identified automatically. They can be moved manually if necessary, by dragging on the green 'handle'.

Lower values will instruct DP to mark as beats only transients with higher amplitudes, while higher values will allow DP to select even transients with lower amplitudes. While the slider gives you control over the general transient/beats ratio in most situations, you will need to manually remove or insert beats in order to achieve a higher level of accuracy, but DP makes it extremely easy to manually change the beats detected. For example, you can suspend or reactivate a beat by simply option-clicking on its handle at the top of the window. To completely delete a beat or a series of beats inside a selected range, use, respectively, the Delete Beat and Delete Beats in Selection functions, found in the Beats menu. To move a beat and adjust its position relative to a transient, simply click and drag it left or right.

Once you're happy with your beats assignment, you can close the Waveform Editor window. At this point, DP 'knows' everything about your soundbite, its tempo and its beats, and you can use this information to accomplish a series of tasks that take full advantage of the new audio engine. For example, you can extrapolate the groove from the selected soundbite, save it as a groove quantisation template and subsequently apply it to a MIDI part, or apply an existing groove to the soundbite without having to slice the soundbite into separate regions.The Adjust Beat Sensitivity slider, from the Beats menu in the Waveform editor, allows you to adjust how many beats DP detects automatically, by changing its amplitude threshold.The Adjust Beat Sensitivity slider, from the Beats menu in the Waveform editor, allows you to adjust how many beats DP detects automatically, by changing its amplitude threshold.

To create a new groove template from a soundbite that has been analysed, simply select the soundbite and choose Region / Create Groove. At this point, the procedure is similar to that used for groove creation from a MIDI part. You can create a new groove folder, Category and Sub-category by navigating though the Create Groove window. The new template created will be accessible through the usual Region / Groove Quantize menu.

Quantising & Groove Quantising Audio Parts

As mentioned above, a really exciting new feature of DP 4.5 is the ability to quantise (and groove quantise) audio soundbites without having to slice them first. This is accomplished by the use of sophisticated algorithms, based on time compression/expansion, that can be applied in a discrete way to each individual beat inside a soundbite. To quantise an audio soundbite, select the soundbite then choose either Region / Quantize or Region / Groove Quantize, depending on the type of quantisation you want to apply. If you choose the former option, make sure to select 'Beats within Soundbites' under the 'What to quantize' option in the Quantization window. When you're quantising the beats of a soundbite, DP will adjust the position of the transients of the audio file according to the quantisation option, and it will time-compress or expand the soundbite in order to make up or reduce the space between transients.

How to Quantise Soundbites

In earlier versions of DP (as well as in version 4.52) you have the option to quantise the beginning of each soundbite. This function is very similar to the one found in Recycle, where a sound file can be separated into different 'slices', according to its transients. Each transient then becomes a separate soundbite that can be moved and quantised independently from the others. In DP you can easily 'slice' an audio file into separate soundbites by using the Scissors tool from the Tools window (bottom tool of the tool bar shown on the right).

  • Open the Graphic editor (double-click on the audio track you want to edit from the Track List window), open the Tools window (Shift-O) and select the scissor tool.
  • You can either create slices using Unit mode (the slices will be inserted only according to the Unit value) or without Unit mode (you can slice your audio file freely). If you need to automatically slice the audio file at regular intervals (let's say every 16th notes), it's best to set 'Unit' to the desired value (in this case, 16th notes) and press the option key while clicking and dragging across the file. A new slice will be inserted every 16th note.
  • Quantise the soundbites/slices you've just created by choosing the normal quantisation function, making sure to set the 'What to Quantize' parameter to 'Soundbites'.

Compare & Analyse Grooves

Comparing the 'feel' of a Peter Erskine drum groove (A) with that of a Jimmy Johnson groove (B), using DP's groove facilities.Comparing the 'feel' of a Peter Erskine drum groove (A) with that of a Jimmy Johnson groove (B), using DP's groove facilities.

An intriguing use for this type of technology is as an analytical tool for comparing grooves, or for showing (to a class, for example) how musicians interpret grooves in different ways. To demonstrate this alternative use of DP 4.5 groove extrapolation/quantisation, I analysed two grooves: one extracted from a Peter Erskine drum library, in which he plays a hi-hat swing groove (pattern A in the screen above), the other from a hi-hat pattern played by Jimmy Johnson in the 1959 Anatomy Of A Murder recording with the Duke Ellington Band (pattern B). In order to analyse the two patterns (played originally at different tempos), I first extrapolated the two grooves, using the beat-detection technique explained above. I created two new quantisation templates based on the beats of each groove, and then inserted two straight 8th-note two-bar patterns on two separate MIDI tracks and applied each of the two groove templates to a different pattern, basically transforming the real groove into a MIDI part. This step was necessary in order to level out the differences in tempo between the two original performances. The results are two two-bar MIDI patterns that can be adapted to any tempo, and that can be compared easily and accurately to each other in terms of where the events happen in reference to bars and beats. In the screen above you can see how Jimmy Johnson's feel is slightly 'ahead of the beat' compared to the feel of the groove played by Erskine. This technique can be applied to other situations where the analysis of a groove is needed.

As you can see, a sequencer and its features can provide a number of new techniques and tools that can greatly improve your sequences and your creative experience. If you explore and let your curiosity guide you, you'll be amazed at the innovative approaches you can evolve.

About The Author

Andrea Pejrolo is a musician and music technology professor, composer, arranger and bass player. He teaches at both Boston's New England Institute of Arts and at Berklee College of Music and has extensive experience of film and television scoring. His book, Creative Sequencing Techniques For Music Production, is published by Focal Press.

Published August 2005