LOGIC NOTES

Custom Groove Templates

Published in SOS February 2002
Printer-friendly version

Technique : Logic Notes

A step-by-step guide to generating custom Groove Templates from your drum loops, plus advice on notating note clusters. And, of course, the usual power-user tips...

One of the most advanced features in Logic is its ability to analyse a drum loop and derive a MIDI Groove Template from it, so that your MIDI parts will gel with its groove. However, like most of the functions within the Sample Editor window's Factory menu, the interface for this is hardly intuitive, and I'm sure it stops a lot of people getting anything usable out of it. So this month, I'm going to show you the tricks I use to get the groove extraction process working for me.

The first thing you have to do is import your drum loop into Logic and trim it to length. Once this is done, you can use Logic's automatic tempo-matching function (I covered this in October 2001's column) to bring the loop into line with the Song's metric grid. You can use the playback loop facility to check that the audio loops smoothly, by highlighting the correct area in the time position bar (Screen 1).

Now double-click the audio region to open the Sample Editor window and choose Audio To MIDI Groove Template from the Factory menu. A floating setup window for this function will come up, and three graphs will appear below the audio of the loop. Reduce all the fields in the setup window to their lowest values, with the exception of the Smooth Release field, which I find is best set to about five percent (this initial setup can be seen in Screen 2). If you now look at the Audio graph under the waveform, you'll see a cluster of little vertical lines for each drum hit (Screen 3). These show where the Factory function is detecting hits -- obviously, with the algorithm's parameters set up as they are, there will be too many of these lines at the moment. Your goal is to tweak the parameters to produce only one detection point per drum hit.

This is easier said than done, but here's my method. Increase the Granulation value (Screen 4) as high as it will go without causing the algorithm to completely miss any points -- up to about 100mS at most. The detection-point clusters will have been narrowed a fair bit (Screen 5). Now you should increase the Attack Range parameter (Screen 6) just high enough to reduce the number of detection points per drum hit to only one (Screen 7) -- but only up to about 50mS at most.

If you can't clean up all the clusters, try increasing the Smooth Release value a little more. If you find that a couple of false detection points are getting through no matter what you do, ignore them -- we'll deal with them in a moment. Finally, reduce the Granulation parameter as far as you can before you start losing detection points that you need. If you still have any stray points, now's the time to click on them with the Pointer tool. This will cause them to be 'greyed out', and they'll therefore be ignored when it comes to creating the Groove Template.

The next thing to do is select a Basis Quantise value which is equivalent to the smallest beat division within the loop (Screen 8). This will make sure that there is a quantisation point for every beat division, even if there is not a drum hit on every beat division of the loop.

Finally, you should set a suitable Time Correction value (Screen 9). I find that the detection algorithm tends to detect drum hits very slightly late, so this parameter can be used to drag all the detection points in the Result graph closer to the actual start of the beat -- you can see the effects of changing this parameter by zooming in and comparing the Audio and Result graphs (Screen 10).

Once all of this has been done, you should select an unused track in the Arrange window and then click the Use button (Screen 11). This does two things: firstly, it creates a muted MIDI object on the selected track in the Arrange window, putting in a note for each of the detection points; and, secondly, it creates a new Groove Template based upon this MIDI object, named after the audio loop which spawned it (Screen 12).

Now you can highlight any MIDI parts you'd like to process with the drum loop's groove and select this Groove Template. At this point the groove is unlikely to be completely on the money, though it may well be close enough to be usable. If it isn't, remember that you can tweak the Groove Template in real time by simply editing the notes of the muted MIDI object from the Matrix Edit window (I explained this in depth in December 2001).

One way I find great for fine-tuning the Groove Template's timings by ear is to play a percussive sound using the muted MIDI object's note data. To get this to work you need first to unmute the object using the Mute tool (the little square one with the 'M' in it) and to put it on a track from which it can trigger a suitable MIDI instrument. Bear in mind, though, that the MIDI notes in the template may be on a number of different channels, so you'll have to make sure that the track instrument channelises the data, or else you'll have to edit the note data from the Event List or Transform window so that it's on the correct channel.

Once you've got the Groove Template notes triggering a percussive sound, select the MIDI object and adjust the Delay field in its Parameters to get the best match -- the MIDI triggering will usually be a little behind, because of the finite time MIDI sound modules take to react to MIDI Note messages. Once you've got things as close as you can get with this parameter, you can sort out any further rhythmic lumpiness by opening up the Matrix Edit window and shifting individual offending notes into line.

Logic Tips     If you use the Transport window a lot, try out the Position Slider available from its pull-down menu. This adds a little bar which shows where the Song Position Line is in the Song, and you can click the bar to move it. This means you can leave the main Arrange window zoomed in to see arrangement detail, and then use the Position Slider to navigate on a larger scale. In the Score window you can double-click any of the Part Box buttons to create a small floating palette of its objects. Furthermore, if you hold down Ctrl or Apple on the Mac while you do this, the little window will be arranged vertically or horizontally -- note that this facility isn't available on a PC. Using a few of these little floating palettes should allow you to switch Parameters off in the View menu for most of the time, giving you a larger window in which to work. There are times when you need a click to count you in for recording, but where having it playing along with you while you're recording is irksome. To sort this out, open up the Recording Options dialogue, from the Settings submenu in the main Options menu, and check the box labelled Click Only During Count-In (Record). Now the click will drop out after the count-in, whether you're using the Speaker Click or triggering a click sound over MIDI using the MIDI Metronome Click object in the Environment.

Notating Note Clusters     If you've been trying to use Logic's Score window for any advanced notation duties, one of the things you may have been fustrated by is the lack of a method for notating note clusters. However, there is a way to do it. The first thing you need to do is create two quarter-note (or shorter) chords. The first should consist of the two outer notes of the cluster along with all the natural notes in between, while the second should comprise all the other notes with accidentals. I find it easiest to create these in the Matrix Edit window. If you're not already in the Score window, then open it now. The first chord you have created will be used to create the visual cluster symbol. Select all the inner notes of the first chord. Using the Attributes menu, select Independent (from the Independent submenu) and Hide (from the Stems menu). Once this is done, drag the square black notehead from the Part Box onto one of the selected notes. The cluster symbol ought now to look correct. However, it won't play back any of the internal 'black' notes of the cluster. This is where the second chord you created comes in. Select all the notes in the second chord and perform the same Attribute-menu changes which you applied to the inner notes of the first chord a moment ago, with the addition of selecting Hide Accidentals from the Accidentals submenu as well. Next, drag the square grey notehead (rather than the square black one) from the Part Box onto one of the selected notes to hide them. As the final stage, combine the two chords by dragging them onto the same beat within the Score window. You should now have a cluster which both looks and sounds the business!

Current Versions     * PC: Logic Audio Platinum v4.8.1. * Mac: Logic Audio Platinum v4.8.1.