As any master carpenter will tell you, before you start any project you need to figure out what's the best tool for the job. Today's technology gives musicians a lot of options. If you've been making electronic music for only a few years, you may have jumped straight into digital audio with sampled loops and plug-in effects. Those are great tools, but there are times when plain old-fashioned MIDI sequencing will give you much more expressive control over your music.
If you've never used the MIDI features of your multitrack recorder, you've come to the right place. In this column, I'll explore how a computer (or a standalone workstation) records and plays MIDI data. I'll also discuss the main ways in which you can edit the data to clean up and personalize your recordings.
MIDI recordings are much easier to work with than digital audio recordings. That is because MIDI tracks contain only performance data, not actual sound. In order to listen to a MIDI track, you have to send it to a MIDI sound module, such as a synthesizer or sampler, which responds to the data by playing notes.
MIDI data is very efficient: a single Note On message, which occupies only a few bytes of computer memory, can trigger a sound that's many seconds in length. Even an old, slow computer can record and play dozens of MIDI tracks at once with perfect timing. The downside is that a Note On message contains no information about what the actual sound will be. The same message could trigger a flute note or a sampled explosion. Or, if the synth on the receiving end isn't powered up, the Note On could result in no sound at all. It's up to you to make sure MIDI playback produces the desired sounds.
The following discussion applies to any MIDI sequencer, whether it's a computer program or a sequencer built in to a workstation keyboard.
Why Use MIDI?
If a sampled loop has exactly the sound you want, there's no need to mess with MIDI. MIDI is the tool of choice when you need to fine-tune the details of a performance. With a MIDI sequencer you can:
* Add filter sweeps and other expressive gestures to a line or just a single note using Control Change messages.
* Change the feel of a drum pattern, subtly or drastically, by changing the timing of MIDI events.
* Create your own beats by triggering individual percussion sounds.
* Try a different lead, bass, or electric-piano sound while keeping the performance (notes and rhythms) exactly the same.
* Change the tempo or transpose a whole song to a new key with absolutely no loss in audio quality.
Though you can use MIDI tracks and sampled (prerecorded) loops or other digital audio in the same piece of music, it's difficult to change the rhythm or tone color of a sampled loop by editing MIDI data. There are some ways to do it, but discussing them would take us well beyond the scope of this article.
The Big Picture
Most sequencers record MIDI data into tracks, which run horizontally across the computer screen in the track or arrangement window. Usually each track is assigned to a single MIDI channel. During playback, all of the track's data is transmitted on that channel, and any synth assigned to that channel will respond to the data by playing the notes recorded in the track. If you don't want to listen to a particular track, you can click on its mute button.
It's important not to confuse tracks (a sequencer feature) with channels (a MIDI feature). In most sequencers, it's easy to assign several tracks to transmit on the same channel. For instance, when building up a MIDI drum part, I often put the kick and snare on one track, the hi-hat part on a second track, and crash-cymbal hits on a third track. All of the tracks transmit on the same channel and are played by the same drum module. By doing this, I can copy and paste a cool hi-hat pattern without having to mess with the kick and snare.
Conversely, you can often find a track setting called Any, which allows a track to transmit data on more than one channel. You can then put data that has several different channel assignments into a single track. Usually there's no reason to do this, but most sequencers will allow it. With a few exceptions, each MIDI message has its own channel assignment. This channel will be overridden by the track's channel assignment unless you set the track to Any.
The MIDI output channel is just one of the playback settings you can make for each track. The most important settings for tracks are listed below. This is an excerpt from the following article: Electronic Musician Tricks for Tracks.
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