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Tips for Tracks

The versatile music-editing features of MIDI sequencers.

By Jim Aikin

Excerpted from Electronic Musician, March 2004

As a 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 only been making electronic music for a few years, you may have jumped straight into the digital audio game with sampled loops and plug-in effects. These are great tools, but there are times when plain old-fashioned MIDI sequencing will give you much more expressive control over your music. In this column we''ll explore how a computer (or a standalone workstation) records and plays MIDI data.

MIDI recordings are much easier to work with than digital audio recordings. This 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, a Note On message contains no information about what the actual sound will be. The very 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, either in the form of computer software or built into a workstation keyboard. If you''re not clear about the various types of MIDI messages, please refer to the Square One column “MIDI Me” in the July 2003 issue of EM.

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 a single note using Control Change messages.

Change the feel of a drum pattern in subtle or drastic ways 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 (pre-recorded) 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.

SEQUENCING: THE BIG PICTURE

Most sequencers record MIDI data into tracks, which run horizontally across the computer screen in the track or arrangement window (see Fig. 1). Each track is usually assigned to a single MIDI channel. During playback, all of the track''s data will be 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 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.

The Big Red Button

Recording music in a MIDI sequencer works very much like recording audio, except that you never have to worry about creating distortion by overloading the input. You put the sequencer in record mode, select (“arm”) the track where you want to record, and then listen to the previously recorded tracks while playing your MIDI keyboard or other MIDI controller. Your performance is captured in the armed track.

As with audio, the MIDI keyboard's output has to be connected to the sequencer's input in order for anything to be recorded. Such amenities as overdubbing, automatic punch-in and punch-out, and loop recording (in which you can keep trying the take over and over until you get it right) are supported by most sequencers. If your keyboard skills are minimal, you can take advantage of step entry, with which you record one note or chord at a time.

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 only one of the playback settings you can make for each track. The most important settings for tracks are listed below.

Transposition. By moving each track (except the drum tracks) up or down in half steps, you can play the music in a different key. By transposing a single track up or down by 12 half steps, you can hear the part in a different octave.

Volume. When playback starts, each track can send a MIDI Control Change 7 (Master Volume) message. A synth assigned to that channel will adjust its output volume based on this message. This is a quick way to set up a rough mix for a MIDI-based song arrangement.

Program Change. When you select a Program Change message (and, if need be, a Bank Select message) for the track, the sequencer will send out these messages on the track''s channel just before starting playback. This insures that each synthesizer will have the proper sound selected.

Velocity scaling. MIDI notes all have Key Velocity values, which can be anywhere between 0 and 127 (though the values you will see in your sequencer are between 1 and 127). In most synths, Velocity is used to make the sound of each note louder or softer. Adjusting all of the Velocity values for a track up or down is another quick way to bring the sound of a synth forward in the mix or reduce it so it blends in better.

Velocity scaling is a better choice than Master Volume when you''ve assigned several tracks to the same MIDI channel, because Master Volume is a global message that will be applied to all of the sounds played by the synth on a given channel. Velocity data is attached separately to each note. With Velocity scaling, for instance, you could boost the level of the hi-hat without affecting the kick and snare on the same channel, as long as the hi-hat is in one track and the kick and snare are in a different track.

TRACK OR TREAT

MIDI sequencing is a mature technology, so most sequencers, even the inexpensive ones, have dozens of sophisticated features. In this article we''ve had room to discuss only a few of the most important types of MIDI edits. All you need is the sequencer owner''s manual, a decent multitimbral MIDI synth, and a little patience, and you''ll be well on your way to making great music.

Jim Aikinwrites about music technology for a variety of publications. He has been composing music with MIDI sequencers since 1985.