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. If you're not clear about the various types of MIDI messages, refer to “Square One: MIDI Me” in the July 2003 issue of EM (available online at www.emusician.com).
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.
FIG. 1: The main track display in Steinberg''s Cubase VST shows track names and other track parameters on the left and the recorded MIDI data extending across the area on the right. Several of the parts have been block-copied by Alt+click-dragging to lengthen the piece of music.
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). 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.
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.
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.
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 ensures that each synthesizer will have the proper sound selected.
MIDI notes all have Key Velocity values, which can be anywhere from 0 through 127 (though the values you will see in your sequencer are from 1 through 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 can 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 a separate track from the kick and snare.
Changing the track playback parameters is a quick, easy way to change the sound of a MIDI sequence, but you can go much deeper. Most sequencers offer several types of editing utilities and editing environments, with which you can bend, shape, mangle, and torment the MIDI data. The editing facilities in workstation sequencers tend to be simpler than those in computer-based sequencers, but some workstation sequencers are quite powerful. Consult your owner's manual for details. The most important types of editing are:
Track window drag and drop
The track window will allow you to separate MIDI data into short segments (variously called chunks, parts, or clips). You can drag these segments to an earlier or later position in the composition, delete them, and copy them. After improvising a 32-bar bass line, for instance, you can separate out the 2-bar phrase you like best using a scissors tool, delete the rest of the take, and copy the 2-bar phrase over and over for the length of the song.
FIG. 2: In the piano-roll edit window in Cakewalk Sonar XL, the keyboard display on the left indicates which MIDI notes have been recorded, and the strip along the bottom shows the note Velocities. Here, the mouse is being dragged across a group of notes (the ones inside the rectangle) so they can be edited.
In the piano-roll window (see Fig. 2), MIDI notes are displayed graphically. The display looks rather like the rolls of paper used in player pianos, except that it runs horizontally rather than vertically. Time runs from left to right, so longer notes appear as longer lines in the display. Pitch runs vertically, with high MIDI notes at the top and low ones at the bottom.
In the piano-roll display, you'll be able to grab single notes or groups of notes with the mouse and drag them around as needed. Another mouse tool can be used for inserting new notes, and a third tool will shorten or lengthen existing notes.
In the notation window, MIDI notes are displayed in the form of conventional rhythmic values on a staff. By printing out the music shown in this window, you can get a lead sheet or a full score for your music. Some musicians prefer to edit their MIDI tracks using the notation display because it's familiar. Notation displays have some drawbacks, however. For one thing, they can show notes only in conventional rhythmic values. A note that has an in-between length (duration) can't be notated accurately without using tuplets or dotted and tied rhythmic values that are hard to read and harder to edit.
Graphic controller editing
After recording a sweep or bend with your keyboard's modulation or pitch wheel/lever, you can edit the controller movement graphically using a pencil tool, as shown in Fig. 3. You can smooth out a move that's a little rough, or lower the peak if it's too high. As in the other editing environments, you can add new data using the pencil tool.
The tool for micromanaging your MIDI data is the event list. Here you'll see a list of all the data in a track, and you'll be able to edit each event (note, Control Change, Program Change, and so on) as desired. For instance, you can lower the Velocity of a single note that you hit a little too hard, shorten a long note, or change the pitch of a wrong note without disturbing its timing.
FIG. 3: The graphic controller-editing display in Cubase is positioned below the piano-roll display, making it easy to see how your controller moves relate to the notes. Here, Pitch-bend data is being edited with the pencil tool.
Computers are capable of very precise timing. The timing of MIDI data in a sequencer is based on the sequencer's pulses per quarter note (ppqn) setting. If the sequencer is running at 480 ppqn, for instance, there will be exactly 480 different time locations available within the space of each quarter note. Every MIDI message in a track will be located at one of these time locations (they're also called clock ticks) and will be transmitted each time the sequencer's master clock reaches that time position during playback.
The sequencer's event list will display the time of each event in a format called bar:beat:clock. For instance, you might see the following:
This says that the MIDI event occurs in bar 7, beat 3, clock tick 120. If the sequencer is running at 480 ppqn, a value of 120 means that this event falls precisely on the second 16th note of the beat. Reading large clock-tick values sometimes requires a little head scratching, but it's not terribly difficult.
If the event described above is, say, a syncopated kick-drum note and if its time is shown as 007:03:129, that means it's a little late compared with an ideal 16th note. You can tidy up the rhythm by lowering the 129 to 120 in the event list, but if you've recorded hundreds or thousands of MIDI notes, editing their timing one note at a time is far too laborious. Fortunately, there's an easier way.
After selecting a group of MIDI notes, which could be an entire track, a single segment in the track window, or a group of notes in the piano-roll window, you can quantize them. When notes are quantized, their start times are moved so that they line up with an evenly spaced rhythmic grid. If your keyboard technique is a little sloppy, quantizing can make you sound like a virtuoso (see the sidebar “The Big Red Button” for a word on recording). Quantizing usually affects only notes, leaving Control Change and other MIDI messages untouched.
The downside of quantizing is that it can make the MIDI performance sound a little too perfect — a bit robotic, in fact. Most sequencers offer features that let you quantize your rhythms without overdoing it. You may be able to set a strength percentage, for instance, so that notes are not locked to the nearest beat, but moved only 50 or 75 percent of the distance between their starting position and the beat.
In swing/shuffle quantizing, notes on the offbeats are delayed by a certain amount. That gives the groove the looser feel that is often heard in jazz and blues styles. The shuffle amount may also be displayed as a percentage value (typically between 50 and 70 percent). It's important not to confuse the shuffle percentage with the strength percentage. The two features have very little in common, except that they both affect the timing of notes.
A more sophisticated option is groove quantizing, in which the timing of notes is corrected to a groove template, rather than to a fixed rhythmic grid. For instance, the groove template might push (advance) the timing of beat 2 in each bar just slightly, giving the backbeat a more aggressive flavor. Using groove templates is a great way to give your MIDI percussion a human feel.
TRACK OR TREAT
MIDI sequencing is a mature technology, so most sequencers, even the inexpensive ones, have dozens of sophisticated features. In this article, I'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.
THE BIG RED BUTTON
Recording music in a MIDI sequencer works in much the same way as 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 in audio recording, the MIDI keyboard's output has to be connected to the sequencer's input in order for anything to be recorded. Your sequencer probably supports 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). If your keyboard skills are minimal, you can take advantage of step entry, with which you record one note or chord at a time.