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MIDI & Digital Audio Music Sequencer Techniques (Part 1)
Written by Scott R. Garrigus - 2005, Scott R. Garrigus. All Rights Reserved.
Music technology has finally gotten to the point where almost anything sonically imaginable can be achieved. Audio can be recorded, chopped into pieces, and then rearranged into something completely different - all with a few clicks of a computer mouse. Whole environments can be simulated so that while it sounds like your singing on stage in a huge concert hall, you're actually standing in the middle of your bedroom studio. Complete professional-quality songs can be recorded, produced, mixed, and mastered using a single standard computer system with MIDI/digital audio sequencing software.

Of course, just because you can imagine something doesn't mean you know how to accomplish it. Today's digital audio sequencers pack so much power and contain feature upon feature, that it's easy to stay comfortable and just stick with the basics, especially when you're facing deadlines and don't have the time to experiment. But that's why you read DigiFreq, right? ;-)

We're going to take a look at some sequencing techniques that you can use in your day-to-day digital audio dealings. We'll cover a number of generic techniques that will work with any sequencing software you may have. I'm going to assume that you already know the ins-and-outs of MIDI and digital audio. Ready? Set? Let's go...

EFFECTS WITHOUT EFFECTS
The real-time effects built into many sequencers aren't the only way to add excitement to your MIDI and digital audio tracks. With a few applications of the copy, paste, and pitch shift commands, you can easily simulate a number of different effects including delay, flange, and chorus. This can free up some of your computer's precious processing power for handling the more complex effects like compression and reverb.

Digital delay. This technique actually covers a number of different effects, and can be applied to both MIDI and audio tracks. Simply copy the MIDI or audio clip that you want to process, and paste it to a new track. Then slide the copied clip forward in time to create a delay. Depending on how much of a time offset you use, different delay- related effects can be achieved. Slide the clip between 5 and 10 milliseconds and you get a thickening effect. Slide the clip between 10 and 20 milliseconds and the thickening turns into doubling. Anything above that amount and you start creating discrete echoes.

If you want to create a delay that is synchronized in time with the music, just move the copied clip ahead by snapping it to a note value such as a sixteenth. To make things more realistic, make a few clip copies and slide each one a sixteenth note apart. Then lower the volume of each successive echo so that the effect fades over time. As an example, for three echoes, lower the volume of the first to 75%, the second to 50%, and the third to 25% of the original. You can even get a little crazy by sliding each copy to a different uneven time offset, and maybe give them different pan positions too. You can't get that kind of precise flexibility with a real-time effect.

Flange. This effect can be applied to both MIDI and digital audio tracks but they require slightly different procedures. As with delay, simply copy your clip to a new track. From here, you can easily produce a static flange effect by moving the copy forward in time from 1 to 5 milliseconds. While this creates an interesting sound, it doesn't have that authentic analog sweeping that we all love and cherish. To achieve that, we need to use a little pitch shifting.

For audio, instead of moving the clip copy, just shift its pitch anywhere from -12 to +12 cents. This will make the copy longer or shorter by a minute amount, causing it to drift out of sync with the original. Of course, depending on how long the clip is, eventually there will be so much of a delay that the flanging will turn into doubling. To get around that, just shift the pitch of small segments of the clip, alternating the direction of the shift with each segment. For example, shift the first two seconds of the clip by -9 cents, the next two seconds by +9 cents, and so on. This is also how you can control the rise and fall of the sweeping characteristic.

For MIDI, the procedure is similar except you need to apply pitch wheel controller changes to the clip copy. Just draw in some pitch controller changes over the course of the clip that vary by rising above and falling below the zero axis. I found it best to stay within the +600 to -600 bend range because any changes larger than that start sounding like detuning rather than flanging. To apply precise changes, many sequencers will allow you to insert a series of controllers that change evenly from a start value to an end value over a set amount of time. This will give you more precise sounding effects but you may prefer the more random fluctuations you can get from just drawing the controller changes in by hand. Either way, the effect is not quite as authentic as with audio. Many times it sounds more like chorusing than flanging.

Chorus. You create audio chorusing in almost the same way as flanging except you need to stretch the pitch, rather than shift it - meaning you need to change the pitch of the audio clip without changing its length. Most programs have this capability. To apply chorusing to an audio clip, simply copy the clip to a new track and stretch its pitch, plus or minus 9 to 12 cents. The more you stretch it, the deeper the effect. You can also use this technique to create a pseudo-stereo effect from mono parts by simply panning the original clip and clip copy to different locations. The more pan, the wider the stereo image.

If you really want to go wild, you can create something I like to call the Super-Combo Chorus Effect. This time, instead of creating just one clip copy, make 3 or 4 or more. Stretch the pitch of each copy using slightly different values from the rest. Now slide each copy in time using the delay techniques described earlier with slightly different values. For the final touch, evenly pan each copy throughout the stereo field. You can also give each copy a different volume level for more subtlety. When you're finished, hit play to experience one very cool chorus simulation.

EFFECTING THE EFFECTS
When destructively applying plug-in effects to digital audio, many sequencers will let you either replace the original material or leave the original material intact and create a new track (or set of tracks in the case of stereo) for the new effected material. If you adjust the levels of the effect module so that the dry mix level is 0% and the wet mix level is 100%, your new track(s) will contain the effect output minus the original signal. Why would you want to do this? Because it gives you some very interesting possibilities.

For instance, you can now control your track effects in a variety of ways. Using volume controllers you can bring the effects track(s) in and out to add an artistic flair to the mix. You can also use panning to move the effected signal around the stereo field while the original signal either remains stationary or moves around as well but independently. Even more possibilities arise when you consider that you can add effects to the effects track(s). How about applying different EQ to the original and effected tracks? If your effected tracks contain reverb, how about applying another reverb effect on top of that for some very far out spatial displacement?

And if you happen to have multiple soundcards or multiple outputs, you can assign your effects track(s) to their own outputs. This way you can even use your outboard modules to add effects to the already effected track(s). Experimentation is the key here.

QUANTIZING AUDIO
You've probably heard of the term "Groove Quantizing" or something similar, where a sequencer uses a pre-defined MIDI pattern that contains data in a specific rhythmic style and applies it to recorded MIDI data so that it conforms to the same rhythm. This feature is a great way to breathe new life into a tune or even give it a different sense of feel.

Well, in case you didn't know it, you can also use "Groove Quantizing" on audio tracks. You just need to do one small preparatory step. You need to break down the audio track (or audio clip) into small pieces or clips. Some sequencers will have an automatic feature for this. If yours doesn't, you can try exporting your track to an audio editing program like Sound Forge. Using Sound Forges' Auto Region and Extract Regions tools, you can easily break down a large audio file into smaller ones that contain a quantizable musical unit such as one beat of data.

When you import the small audio files back into your sequencer, each one will have its own start time, just like a MIDI event. This lets you easily quantize the playback of the audio segments, and you also don't get the weird anomalies that can arise from trying to stretch the audio. This technique works especially great with percussion clips but don't rule out instrumental or even vocal clips. Try turning a normal vocal track into a cool rhythmic scat. It's a lot of fun!

For more information:
* Sequencer Techniques (Part 2)
* Power! Books


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