Step Sequencer Basics

An analog tool from yesteryear transitions to digital—and learns a few new tricks in the process

By Craig Anderton

Step sequencing has aged gracefully. Once a mainstay of analog synths, step sequencing has stepped into a virtual phone booth, donned its Super Sequencer duds, and is now equally at home in the most cutting-edge dance music. In a way, it’s like a little sequencer that runs inside of a bigger host sequencer, or within a musical instrument. But just because it’s little doesn’t mean it isn’t powerful, and several DAWs include built-in step sequencers.

Early analog step sequencers were synth modules with 8 or 16 steps, and driven by a low-frequency clock. Each step produced a control voltage and trigger, and could therefore trigger a note just as if you’d triggered a keyboard. The clock determined the rate at which each successive step occurred. As a result, you could set up a short melodic sequence, or feed the control voltage to a different parameter, such as filter cutoff.

Step sequencing in a more sophisticated form was the basis of drum machines and boxes like the Roland TB-303 BassLine, and is also built into today’s virtual instruments, such as Cakewalk’s Rapture, and even as a module in processors like Native Instruments’ Guitar Rig (Fig. 1).

Fig. 1: Guitar Rig’s 16-step “Analog Sequencer” module is controlling the Pro Filter’s cutoff frequency.

Reason’s patch-cord oriented paradigm makes it easy to visualize what’s happening with a typical step sequencer (Fig. 2).

Fig. 2: This screen shot, cut and pasted for clarity, shows Reason’s step sequencer graphic interface, as well as how it’s “patched” into the SubTractor synthesizer.

The upper Matrix view (second “rack” up from the bottom) shows the page generating a stepped control voltage that’s quantized to a standard musical scale as well as a gate signal; these create notes in the SubTractor and trigger their envelopes, as shown by the patch connections on the rear. The lower Matrix view is generating a control voltage curve from the Curve page, and sending this to the SubTractor synth filter. The short, red vertical strips on the bottom of either Matrix front panel view indicate where triggers occur.

THIS YEAR’S MODEL

Analog step sequencers typically had little more than a control for the control voltage level, and maybe a pushbutton to advance through the steps manually. Modern step sequencers add a lot of other capabilities, such as . . .

Pattern storage. Once you tweaked an analog step sequencer, there was nothing you could do to save its settings other than write them down. Today’s sequencers usually do better. For example, the Matrix module in Reason stores four banks of 8 patterns, which can be programmed into the sequencer to play back as desired.

Controller sequencing. Step sequencers aren’t just for notes anymore, and it’s usually possible to generate sequences of controllers along with notes (Fig. 3).

Fig. 3: A row in Sonar’s Step Sequencer triggers notes, but you can expand the row to show other controller options. This example shows velocity editing.

Variable number of steps. Freed from the restrictions of hardware, software step sequencers can provide any number of steps, although you’ll seldom find more than 128—if you need more, use the host’s sequencing capabilities.

Step resolution. Typically, with a 16-step sequencer, each step is a 16th note. Variable step resolution allows each step to represent a different value, like a quarter note, eighth note, 32nd note, etc.

Step quantization. With analog sequencers, it seemed almost impossible to “dial in” particular pitches; and when you did, they’d eventually drift off pitch anyway. With today’s digital versions, you can quantize the steps to particular pitches, making it easy to create melodic lines. The step sequencers in Rapture even allow for MIDI note entry, so you can play your line and the steps will conform to what you entered.

Smoothing. This “rounds off” the sharp edges of the step sequence, producing a more rounded control characteristic.

WHAT ARE THEY GOOD FOR?

Although step sequencers are traditionally used to sequence melody lines, they have many other uses.

Complex LFO. Why settle for the usual triangle/sawtooth/random LFO waveforms? Control a parameter with a step sequencer instead, and you can create pretty whacked waveforms by drawing them in the step sequencer. Apply smoothing, and the resulting waveform will sound more continuous rather than stepped.

Create rhythmic patterns with filters. Feeding the filter cutoff parameter with a step sequencer can provide serious motion to the filter sound. This is the heart of Roger Linn’s AdrenaLinn processor, which imparts rhythmic effects to whatever you send into the input. If the step level is all the way down, the cutoff is all the way down and no sound comes out. Higher-level steps kick the filter open more, thus letting the sound “pulse” through.

Polyrhythms. Assuming your step sequencer has a variable number of steps, you can create some great polyrhythmic effects. For example, consider setting up a 4-step sequence (1 measure of 4/4) in one step sequencer, and a 7-step sequence (1 measure of 7/4) in a second step sequencer, each driving different parameters (e.g., filter sweeps in opposite channels, or two different oscillator pitches). They play against each other, but “meet up” every seven measures (28 beats).

Double-time and half-time sequences. By changing step resolution in the middle of a sequence, such as switching from 8th notes to 16th notes or vice-versa, it’s possible to change the sequence to double-time or half-time respectively.

Complex panning. Imagine a step sequencer generating a percussive sequence by triggering a sound with a very quick decay. Now imagine a step sequencer altering the pan position for each hit – this can add an incredible amount of animation to a percussion mix.

Live performance options. The original step sequencers were “set-and-forget” type devices. But nowadays, playing with a step sequencer in real time can turn it into a bona fide instrument (ask the TB-303 virtuosos). Change pitch, alter rhythms, edit triggers . . . the results can be not only hypnotic, but inspiring

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.