Recording - July 2010 - 20

only format. apTrigga had a good set of features, and Drumagog had a very comprehensive set of features, but with both I wasn’t sure I would be able to adapt the EXS-based drum Instrument to a plug-inonly solution that would bypass the specific programming within the EXS sampler plug-in(s) required for the most expressive dynamic response; Drumagog in particular seemed very capable in this regard, but

Figure 6: False triggers (low-level notes that don’t belong) in Audio-to-Score, deleted by mouse-clicking them. MIDI tracks to trigger the replacement samples. The other way was to hand off the conversion to a dedicated drum-replacement plug-in, which would take in the original audio stream and spit out a string of replacement hits, again with appropriate velocities. Under the hood, both options do basically the same thing: the transients of each original drum note are detected and used as triggers for the samples to be substituted—the transient levels are interpreted and applied to duplicate the dynamics of the original performance. Of course, in practice it gets a bit more complicated than that, as we’ll see, but the methodology is pretty straightforward. Since I hadn’t done a major drum replacement session for some time, I did a brief survey of the available tools, to see what might be the fastest and most accurate option currently. There are a lot of choices nowadays, but I quickly narrowed them down to five: • Drumagog, fromWaveMachine Labs, a plug-in that seems to be on everybody’s AList for this kind of work; • apTrigga, from apulSoft, another popular, relatively inexpensive, drum replacement plug-in; • Drum Rehab, from Trillium Lane, a ProTools-compatible plug-in; • Logic 9’s new built-in Drum Replacement function; • Logic’s older (also built-in) Audio-to-Score function. Making a choice The songs were supplied as Logic Project files, so that eliminated the use of the Drum Rehab plugin, due to its Pro Tools20
RECORDING JULY 2010

not without a fair bit of extra work prepping the samples to duplicate the effect of the EXS processing. Since the studio didn’t own any of the plug-ins mentioned, and since the songs were already in Logic format, I decided to try Logic’s built-in solutions first, and only go to one of the plugins if that proved too slow or problematic.

The studio where the project was being mixed was still using Logic 8 at the time, so I decided to do a test in Logic 9, at home, of its new dedicated Drum-Replacement feature, and then try the same song with Logic 8’s older Audio-to-Score option (still in Logic 9 as well), before suggesting an upgrade in the middle of the project (never a wise move!). After checking out both, I decided to do the work with Audio-to-Score—it seemed to me to use pretty much the same engine under the hood, but the new DrumReplacement feature had been significantly streamlined to speed up the process and make it more accessible to someone who wasn’t overly familiar with the somewhat tweaky adjustments involved. In this case, due to the significant leakage on the tracks, I felt flexibility was more important than speed (it was obviously going to take quite a bit of manual fine-tuning anyway), and the lack of automated functions in the older option was actually an advantage with the customized drum Instrument we were using, since it provided a raw MIDI sequence which could then be tweaked with the greatest flexibility for accuracy and performance. We ended up doing the entire project with that basic Audio-to-Score feature, and even though it was fairly time-consuming, the end results were worth the effort. But to make this discussion more universal, as I describe the specific steps and adjustments done, I’ll also mention how those same tasks would have been accomplished with the other drum-replacement tools we could have chosen for the job (with a sampled drumkit that used more standard programming, one of those choices might have made more sense). So, here goes. [We know some of the figures are a bit small; you can download larger versions from our website. Go to our Resource Library and look for this article under Magazine Extras/ Article Illustrations.—Ed.] Step by step The basic steps in the drum replacement procedure are pretty straightforward: • Identify notes—this is done mainly by transient detection, as used in other audio editing tools like the Elastic/Flex/Warp features in various DAWs that allow for time compression/expansion. • Separate “good” notes from “bad” notes—“good”, of course, being the notes of the main instrument in that track that’s due to be replaced; “bad” notes would be notes from other instruments that don’t belong, such as snare drum leakage into a kick drum track, for example. This step is often where problems first come up, and is key to getting a proper replacement part. • Translate the dynamics of the original performance to the replacement sound— this is critical in preserving the sense of a live performance, with all its subtleties and nuances. The drum-replacement plug-in or

Figure 7: Drum Rehab’s Add feature allows manual insertion of note triggers (with the proper velocity).

Figure 8: Audio-to-Score’s timing offset (Time Correction) setting.
Recording - July 2010

Table of Contents for the Digital Edition of Recording - July 2010
