Give Digital Synth Sounds An Analogue Feel

Analogue synths tend to have less high end, due to the signal going through a low-pass filter at all times. Digital synths have a pretty extended high end and their higher frequencies are somewhat more distortion-prone, which can give a raspy sound instead of the duller, warmer analogue sound.

Anything that cuts highs slightly from your digital synth will help warm it up, including tone controls, outboard equalisers, simple tube preamps, and mixer hi-cut filters. At first the sound will seem dull by comparison, but let your ears get acclimatised. Not every sound needs high-frequency 'zing' (just ask any guitarist playing a Les Paul through a stack of Marshalls). In fact, you can often bring duller sounds up more in the mix (great for leads) without their sounding harsh or strident.

One of analogue's charms is the slight detuning that occurs when component values drift because of ageing, temperature fluctuations, changes in planetary positions, and whether the refrigerator just kicked in next door. This drift is most noticeable with multiple oscillator patches, as it creates a 'humanised' chorusing effect.

"Anything that cuts highs slightly from your digital synth will help warm it up..."

Digital synths have inherently perfect tuning, but an easy antidote is to assign velocity or pressure (or both) as pitch modulation sources. The amount should be very small -- just a few cents variation -- and one oscillator should go slightly flat while the other goes slightly sharp (negative and positive modulation respectively). As you play, small pitch changes will occur that add more character. (Some Yamaha FM synths, including the TX802 and DX7 MkII, had a built-in pitch-randomising option. However, I prefer variations that correlate to your playing. It may be less analogue, but it's more expressive.)

Layering analogue waves with sampled ones can work wonders. For example, remember those smooth, dreamy string synthesizer sounds of the '70s? They were usually based on pulse and sawtooth waves. Layering these with real string samples produces a result that's more smooth and analogue-sounding than the sampled version, but seems thicker and more realistic than the purely analogue waves.

Many digital synths offer a monophonic keyboard mode where only one note plays at a time, just like the vintage, steam-powered synths that were all the rage during the 1840s (just kidding). This really helps get you into a Minimoog mood, but also note that in most cases this mode also allows for portamento. In fact, that sound has become so identified with analogue synths that adding a bit of portamento to just about any digital sound makes it seem more analogue.

Even when set for minimum attack, no sustain, and instant decay, the Minimoog envelope exhibits a slight hold time at maximum level before the decay starts. I believe this is what gives the Mini its punchy sound, as it hits your ears full blast for a little bit at the beginning of the note -- not unlike limiting.

With sustained sounds, you can create the same effect with any digital synth, using time/level envelopes: set the first two levels to maximum, and programme a bit of a hold time (around 20-30ms) before the rest of the decay kicks in.

If your synth doesn't read out time in milliseconds but instead uses SANs (Stupid Arbitrary Numbers), don't panic. After setting the first two levels at maximum, turn the other levels all the way down. Next, adjust the time between the first and second levels (called 'T1' on most envelope generators) for a bit more duration than a click, but less than an obvious note or tone. Finally, program the rest of the envelope. Figure 1 shows a typical 'punch' envelope, with the hold time indicated in yellow.

Early analogue drum sounds were based on a variation of the 'Twin-T' oscillator circuit (a sine-wave oscillator set just below the point of self-oscillation). When hit with a trigger pulse, the circuit would oscillate briefly, creating a damped sine wave that decayed logarithmically over time. This is why the analogue kick drum on a TR808 is so deep: it's a very low-frequency sine wave (almost like 60Hz hum) with no harmonics at all -- just pure bass.

To recreate the 'hum drum' patch digitally, start off with a sine wave and set the amplitude envelope for a logarithmic decay (that's a rapid initial fade, then a slower fade toward the end). Also consider layering a percussive attack (a wood block tuned down in pitch, the first few milliseconds from a sampled kick drum sound, or something similar) along with the sine wave to add a bit more edge.

Digital synths (with few exceptions) lack the same kind of control complement as analogue synths. But many parameters can be assigned to respond to MIDI continuous controllers or SysEx commands, and MIDI hardware controllers such as the Peavey PC1600 provide sliders that can send out continuous controller or SysEx information. Although this requires some programming in advance (programming SysEx strings is particularly challenging; if you don't have your synth's SysEx implementation, write and ask the manufacturer for a copy), it's an effective way to obtain real-time control over multiple synth parameters. Also, a synth's data slider can often control a particular function (and don't forget about the footpedal jack).

The bottom line: yes, analogue synths are fun. But just as analogue synths were under-utilised when they were the only game in town, digital synths are now similarly under-utilised. Perhaps 20 years from now people will more fully appreciate today's machines, but you don't have to wait until then. I hope these tips will help give your digital recording setup a bit more of an analogue veneer.

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