Secrets Of Expressive Sequencing, Part 2

Primer

Published in SOS June 1994
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Technique : Sequencing & MIDI Controllers

Expressive sequencer parts for monophonic instruments like bass and wind can be difficult to achieve -- unless you understand how bass and wind players approach their instruments and how your sequencer's facilities can help you do the same thing. CRAIG ANDERTON explains. This is the last article in a two-part series. Read Part 1.

 

Last month, I passed on some tips to help you produce more expressive and realistic sequenced guitar and drum parts. This month, we'll take a look at wind and bass parts.

GOOD WIND PARTS: NOT JUST HOT AIR

Good wind players caress each note. Changes in attack, level, and timbre create a very expressive melodic line that is difficult to synthesize electronically in real time. A good wind player with a wind-to-MIDI converter is your best bet for getting expressive wind instrument sequences, but if your only choice is to record the part using a keyboard, there's still plenty you can do to coax your synths into sounding more wind-like.

One Note At A Time: Most wind instruments are monophonic; unless your keyboard offers a monophonic mode, though, the end of one note can often overlap the beginning of the next.

Different sequencers have different ways to create monophonic lines. For example, Performer lets you select "Move releases to the closest attack" in the duration menu; this prevents notes from overlapping. To insert some 'breaths', select the notes after which you want the breaths, then use duration again to set the duration of the selected notes to 90% of their current values.

Figure 1 shows how to do this with Cubase. The quantise parameter dialogue box lets you set the number of ticks by which notes overlap; entering a negative value creates a gap between notes (in this case, 60 ticks). The top note grid shows the unedited line. Notes 1, 3, and 5 overlap the attacks of notes 2, 4, and 6 respectively. If you select these notes and invoke the Legato edit option, notes 1, 3, and 5 end 60 ticks before the start of notes 2, 4, and 6, as shown in the lower note grid. You can select the entire track, but this means that each note off will be changed to create a 60-tick gap between it and the next note-on. This may stretch notes you don't want stretched. The same thing happens with Performer.

To spice things up even more, do a little note-by-note editing. For example, after long notes leave a little more space before the next one so your 'player' can breathe. On fast passages, tighten up the gaps if needed.

One Instrument At A Time: Avoid playing polyphonic wind parts. Record each line (assigned to a different MIDI channel) into the sequencer individually. This lets you add slightly different pitch bend, modulation, pressure, and so on, to each sound for a more realistic overall effect.

Bend Me, Shape Me: One characteristic of most wind instruments is that they don't stay on a constant pitch. 'Drawing' in some low-level pitch bend messages toward the end of a sustained note can simulate this effect. It's usually not necessary to draw a curve and generate lots of data; just a few blips here and there will do the job.

Also try adding some upward pitch bend at the beginning of notes to imitate the effect of a player not starting right on pitch, but bending up over time. You can do this with a pitch bend envelope or pitch wheel, but 'drawing in' bend data lets you make really subtle changes.

Pitch isn't the only parameter worth controlling: volume, waveform, filter, and envelope time changes are also important. It's difficult to play all these controllers at once, which is why post-performance sequence editing can be so useful -- you can literally add 'layers' of expressiveness with multiple controllers. However, real-time control adds a certain magic that you don't get in any other way. Using footpedals for, say, volume and filter cutoff leaves your hands free to add pressure and pitch bend.

Since all these controllers fatten up the MIDI data stream, use controller thinning algorithms to eliminate redundant data. Level can usually be thinned more radically than pitch bend or filter sweeps.

BASS, THE BOTTOM LINE

As with wind parts, bass parts are often monophonic. Therefore, the tips discussed for making wind instruments monophonic also apply to bass.

Let It Slide: Probably the most important part of making bass parts seem 'real' is the judicious use of slides. Whether fretless or fretted, bass players often move from one note to another by sliding, as well as using longer slides for accents (for example, sliding down an octave and 'landing' on the tonic at the same time that the kick drum hits).

As with so many other aspects of sequencing, there's a relationship between the sequencer and the sound generators being driven. Set your bass patches to respond to a pitch bend range of ±12 semitones, as this allows for slides up to two octaves.

Fretless bass parts are the easiest to emulate, since the slide isn't 'quantised' by the bass's frets. Players with good wheel technique can simply move the pitch bend wheel as they play to do fretless parts. However, this is quite tricky with large pitch bend ranges, and it may be difficult to obtain the desired degree of pitch accuracy.

Alternatively, you can play the bass part without slides, then draw them in later with pitch bend messages. This works because most slides end by plucking a new note anyway, so all we really need to do is add slides between existing notes.

To draw in messages with the appropriate bend amount, it helps to make a chart of what pitch bend values correspond to which notes of an octave. (Note: The chart in Figure 2 assumes a linear pitch bend response at the synth.)

There are three columns because different sequencers show pitch bend data differently. Mastertracks Pro 5, for example, shows these values as ±127, Performer as ±8192, and with large-sized windows Cubase 'splits' 8192 so that no pitch bend corresponds to 4096, maximum bend up is 8192, and maximum bend down is 0.

Suppose we want to add a slide that goes from the tonic to the fifth, as shown in the last two beats of Figure 3 (measure 2, beat 1 and part of beat 2). Just draw in a slope that ends at the appropriate value (for example, if your sequencer follows the convention in column 1 of the table, end the slope at 74). Then add a pitch bend = 0 message just before the fifth plays. If necessary, extend the note being slid so that its duration equals that of the slide. (Also note that many sequencers have functions that let you smooth the slope for a bionically-perfect slide.)

One warning: when extending the note, end it before the pitch bend returns to 0 or you may get a pitch glitch (although sometimes this can sound cool). This also implies having a very short -- almost non-existent -- release time on the patch. Program the patch so that the initial decay and sustain parameters control the duration, not the final release.

Time To Fret: Fretted bass slides are a little more complex, but adding this effect can create a stunningly realistic part that has the listener wondering "is it a synth or an extremely consistent and accurate bass player?"

You have two main options for emulating a fretted bass. The first requires a synthesizer with legato mode (Yamaha TX81Z, Yamaha TX802, Ensoniq EPS 16+, Peavey Spectrum Bass, etc.). What this means is that if the durations of two notes overlap, the second note will change the pitch, but not retrigger the note's envelopes -- just like sliding on a fretted instrument (by the way, this is why legato mode is so crucial for use with MIDI guitar and bass).

The first two beats in Figure 3 show one way to create a fretted bass slide. Add notes in semitone steps between the 'source' and 'target' notes, but make sure that the note durations overlap until you hit the target note (which you do want to retrigger).

To create the slide, enter notes in step time with 100% 'articulation' (i.e, if the step-time interval is eighth notes, then each note should be an eighth-note long). Then use a 'change length' command to set each note to 110% of its original length. This ensures that the end of a note will overlap the attack of the subsequent note, thus producing the legato effect in synthesizers that are so equipped.

If your synth does not include a legato feature, write the manufacturer and complain so they'll add it in the next update! Meanwhile, you can create fretted slide effects by extending a note's duration to the length of the slide, and using evenly-spaced pitch bend messages to change pitch. This produces roughly the same effect as having legato mode on the synth, but requires more work. (By the way, sometimes the synth's response isn't fast enough to give the sound of discrete steps, which precludes using this method.)

Figure 3's middle two beats show the same examples as the first two and last two beats, except that discrete pitch bend messages are used to add 'frets' to the slide (note the 'stair step' in the pitch bend graphic). The message values are derived from the table.

The moral of the story: with bass parts, sometimes it's better to just let things slide. And with those words of pseudo-wisdom, it's time to sign off and... get back to doing some more sequencing, of course!

 

IT'S TIME TO SPLIT

Recording individual lines can be time-consuming, so if you have deadlines looming, you'll probably decide to play an ensemble wind part polyphonically and record it on one MIDI channel. You can still make the part more interesting by 'pulling out' individual lines within the chords, and increasing the velocity of these notes. You might be able to split off a part with conditional editing by specifying only notes within a certain pitch range. Otherwise, you may need to dig into the piano-roll screen or event list and, assuming your sequencer allows discontiguous selection, select the events, then do a velocity increase. If discontiguous editing is not available, edit each note individually.

A quicker option is to randomise the start times a bit so that the attacks don't all hit at the same time (a little randomised velocity can help too).

This is the last article in a two-part series. Read Part 1.
More In This Series:

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