- Most software synthesizers employ a subtractive synthesis approach to sound design, combining waveforms with rich harmonic structures (or deliberately limited ones) before removing unwanted frequency content at the filter stage. But LinPlug's Spectral, which recently got some key new features in its Version 1.1 update, uses modulation synthesis instead. Frequency modulation synths like Yamaha's classic DX7 do this, but FM is only one of the ways in which Spectral can modulate its own waveforms, with further options dramatically extending the range of sounds that can be produced here.
At Spectral's core are four independent oscillators, each feeding a dedicated filter. Clicking on the waveform of an oscillator in the top-left corner produces a spectral view of the harmonics present, and you can draw over this to produce the combination of harmonics you want. However, each oscillator actually allows you to create two waveforms, with a mix dial setting the balance between these. Below the buttons on the left, which show which oscillator is currently selected, you can also tune each one in both semitones and cents. Usefully, a spanner button, next to the power on/off switch for each oscillator, allows you to copy settings from one oscillator module to another, making it possible to quickly produce unison-style sounds. This approach appears throughout Spectral, and you can also easily copy-and-paste filter, envelope and LFO settings (plus many more).
Once you've created and balanced the waveforms of the oscillators, each can be further enhanced within the Spread section. First, there's a voices control that adds new copies of the oscillator output, detuned from the original, to produce thicker sounds. The tuning of these copies can also be controlled with dials for width, loudness and spread across the stereo field. While heavy use of Spread significantly increases the CPU demand, a pleasing range of sounds is available as a result.
The next stage is to add cross-modulation, whereby oscillators can benefit from AM (amplitude modulation), FM (frequency modulation) or PM (phase modulation). You choose a modulation type and a target for both sources, then use the amount dial to introduce the modulation depth you want. The only omission here is a dedicated noise oscillator, but that's not to say noise effects can't be generated—you can produce very interesting sounds by dedicating one of your oscillator sources to a noise-based waveform and using Spark's phase modulation abilities.
Each oscillator is linked to its own filter, but as you might expect given the design of Spectral's oscillators, the filters are highly unique. Rather than offering default modes (like low-pass and high-pass), you can draw the filter shapes, detailing precisely which harmonics from each oscillator will be heard in full or timbrally reduced. Additionally, there's a more standard 18-dB low-pass filter to further shape the tonal response of each sound, while envelope settings, key-tracking and more can be configured, too. The cross-modulation possibilities of the oscillators are echoed here as well, with both filter frequency and resonance available as modulation sources. There's also a dial to select the amount of cross-modulation.
Directly from the Filter section, you can freely route each Oscillator to two of six possible effects modules. In other words, though Filter 1 might route to FX 1 and FX 4, Filter 2 could route to FX 2 and FX 3. The dial in the bottom-right corner of the filter allows you to switch between two sources, while the bottom-right corner of Spectral's overall interface lets you configure these. Each of the six slots can be selected, and effects parameters then appear to the left, including choosing effect types from this list. As well as six insert effects, there's also a master EQ section. The effects are great, and where appropriate, they can easily lock to your track's tempo.
The area to the left of the effects section is dominated by the arpeggiator, which allows you to create a running sequence of up to 32 steps. Each step can be assigned a unique velocity value and transposition offset; it can also be changed in length or set to glide to the following step. As you'd expect, the arpeggiator clocks to tempo at the speed of your track (1/8 notes, 1/16 notes, etc.), and there's also a swing control. The arpeggiator has a range of modes, from standard up-and-down patterns to random and chord options. You can also decide the number of octaves over which the pattern will play, so anything from minimal, controlled sequences to ordered mayhem can be achieved.
Envelope and modulation routing modules are configured similarly to the oscillators, selectable one at a time. Below the oscillators, you can click to select the amplifier or modulation source you want before configuring their dials and parameters. The central portion of the entire interface provides a modulation matrix where these routings can be further organised, with each slot providing a modulation source, an amount and a target. You'll find 24 slots, and the range of options is enormous, with sources including all of the expected synth parameters as well as MIDI controllers, the modwheel and velocity, and targets offering every part of the synth engine. These are neatly organised into sub-groups, so you won't be baffled by an endless list. Whereas the envelopes to the left combine with oscillator sources, those below the filter provide dedicated envelopes for shaping the cutoff of each filter source, as well as providing access to the onboard LFOs.
Spectral is an impressive synthesizer capable of unique sounds. Indeed, it makes complex and less well-known approaches to synthesis more accessible. However, as you might be able to detect from its description above, it rewards those who are prepared to do some serious exploration—I can't think of another plug-in which directly emulates its workflow. That said, the comprehensive presets work well as a starting point for your own sounds. My only criticism would be that the Spectral logo, written next to the instrument's name at the bottom of the interface looks too much like Apple's spinning beachball—which OS X users will readily associate with system crashes. When you catch it out of the corner of your eye, it's easy to suffer a momentary pang of horror and to assume that your DAW has locked up, which isn't hugely welcome. This tiny design flaw aside, I'd certainly recommend Spectral to those seeking an unusual approach to sound creation.
Ratings:
Cost: 4/5
Sound: 5/5
Versatility: 4.5/5
Ease of use: 3/5