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Understanding Envelopes, Part 2

By Francis Preve
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Last week, we covered the essential components of an ADSR envelope and the purpose of each envelope segment.

This time around, we’ll touch upon envelope looping as well as more complex multistage envelopes.

After that, we go deeper into the sound design possibilities of modulating various synthesizer functions like filter and pitch.

Envelope looping

Some products include a feature that causes the loop to repeat, allowing you to create complex rhythmic effects similar to those of LFOs.

Certain softsynths also include the ability to synchronize this looping to various note values, like quarter-note, eighth-note and sixteenth-note.

Looped, tempo-synced envelopes were tailor-made for club music, so if your synth supports this function, it’s a deep source of creativity and inspiration worth exploring.

Multistage envelopes

Multistage envelopes go beyond the ADSR format, allowing for complex shapes that swoop and undulate every time a key is pressed.

The first commercially available synth to include multistage envelopes was Yamaha’s legendary DX7, which included rate and level parameters for each stage, allowing for extremely intricate envelopes.

Modern softsynths, like Native Instruments’ FM8 and Massive, include multistage envelopes (pictured above) that are capable of complex morphing and rhythmic effects.

Once you have a mastery of basic ADSR envelopes, the complexity of a multistage envelope may become irresistible.

Fortunately for Ableton Live users, the sequencer’s clip envelope feature provides much of this same functionality in a very intuitive and flexible manner.

Envelope destinations

The three most common destinations for envelope modulation are amplitude/volume, filter cutoff and pitch.

Amplitude/Volume

Every synth includes some sort of volume envelope, otherwise each sound would sustain indefinitely!

As the name suggests, this type of envelope controls how the loudness of a sound will change over time.

Filter envelope

Many synths also include a dedicated filter envelope, which controls the behavior of the cutoff frequency.

By manipulating the segment times and overall envelope amount, it’s possible to create swells, wah-wah effects or enhance the percussiveness of a sound.

Raising the resonance of the filter and applying envelope modulation to the cutoff, results in more dramatic, funky and/or squeaky effects.

Some filter envelopes also include a bi-polar or invertible amount control.

If an envelope is inverted, it will begin with a decay, followed by a rise (second attack) to the sustain level, and finally, when the key is lifted, a final rise to the original cutoff value.

Note: When working with the filter envelope, it’s important to keep in mind that the envelope will add or subtract from the current cutoff frequency setting, so if the cutoff is set at maximum and the envelope amount has a positive value, you will not hear its effect since the cutoff is already at full value.

Conversely, if your cutoff is set to minimum and the envelope amount is a negative value, then the envelope will have no effect for the opposite reason.

Pitch envelope

Sometimes a third envelope is included for pitch or other modulation possibilities.

Alternately, some synths allow the filter envelope to also modulate pitch.

In either case, a pitch envelope will affect the tuning of one or both oscillators.

With a moderate amount setting and fast segment times, a pitch envelope can enhance the attack and/or add an organic quality to a sound.

More extreme settings can be used to create those electro sound effects that run the gamut from squeaky to wild pitch sweeps.

If electro is your cup of tea, I highly urge you to start with a single sawtooth oscillator, set the lowpass filter cutoff to maximum, then go crazy experimenting with the pitch envelope options.

You’ll be pleasantly surprised.

Other parameters

In some synths, like the Prophet 08, Reason’s Thor, and Ableton’s Sampler, the third envelope can be routed to many other destinations besides pitch.

Here are a few possibilities.

FM amount: If an oscillator or filter can be modulated via FM (frequency modulation), you can create extreme effects by using an envelope to shape this amount over time, resulting in percussive or sweep effects.

LFO amount: Sometimes, it can be cool to use an LFO to add a touch of vibrato to the beginning of a note or have it fade in as the note evolves, this can be done with an envelope.

Hard sync: Classic hard sync sweeps – an effect that sounds a bit like an extreme flanger – can be created by activating hard sync and modulating the pitch of the slaved oscillator only.

Not sure which oscillator to modulate?

Just activate oscillator sync, create an extreme envelope with a medium attack and decay, and apply the envelope to each oscillator individually (with high amount values).

If the envelope sweeps the overall pitch, that’s the wrong destination.

If you hear a crazy “ripping” sound, that’s the correct oscillator, so make a note of it.

So there you have it, the essentials of envelope modulation.

Next up… LFO madness!