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The Dark Side

Reason Tips & Techniques
Published April 2013
By Robin Bigwood

Explore the secret paths to modulation on the dusty reverse of Reason's cheery fascia...

Reason doesn't have an auto-pan device, but you don't need one as long as you know some simple CV techniques.

When you're starting out with Reason, or just want fast results, the colourful, friendly front panels of devices are all you need. Patch selection, tweaking, programming, automation: it's all there. But hit the Tab key, flip the rack around, and suddenly you enter a whole new world of flexibility. Now it's all sockets and patch cables, like modular analogue synths of old. You can make specialised audio routings and, by drawing cables between the slightly smaller CV (control voltage) sockets, modulate parameters and trigger events in ways that would otherwise be unachievable. It's this aspect of Reason we'll focus on in this month's column.

CV Duties

Let's start simple. Say you've recorded an electric guitar on an audio track and you want to apply some auto-pan. No effects devices amongst Reason's bundled assortment will help you, but the powers of CV can come to the rescue. What we need is something that can produce a regular oscillation — a synth's LFO — and to apply that to the pan position of the audio track. Here's how it works.

Right-click in an empty part of the rack near your guitar track's Audio Track device and create a Subtractor synth; its LFO1 is going to be the CV source. Keeping the Shift and Alt keys held down as you do this prevents Reason from giving Subtractor both a Mix device and a sequencer track, which, as we're only using the Subtractor for its LFO, is what we want.

Press Tab to view the rear of the rack. Click and drag a cable from the Subtractor's LFO1 CV Socket (in its Modulation Output section) to the Audio Track device's CV IN socket, next to its Pan knob. That's all there is to it, but to control the auto-pan effect you can tweak Subtractor's LFO (on its front panel) to set the Rate of oscillation, and also its shape via the Waveform selection. The Amount knob does nothing here, so look to the Audio Track device's rear-panel Pan knob to adjust the depth of the effect.

This is a classic, simple CV patch, and it's just the start of what's possible. Now let's have a look at some other useful CV sources and destinations.

Instruments Of Change

Malström's MOD LFOs can create all manner of interesting modulation shapes which, via CV connections, can be applied to other devices.

All of Reason's built-in instruments, except for NNXT and the little ID8 preset player, can be used as CV sources. Their LFOs (as we saw in the auto-pan example above) are always useful, but they're not all created equal. For example, Thor's offer 18 different waveforms, including a number of quantised or stepped options. Malström's 'MOD' LFOs have even more — 32 waveforms. That would be some funky auto-pan! The point is that if you're designing a sound in Subtractor, say, but you wish you had one of Malström's LFO shapes available, well, you do. Create a Malström, flip the rack, and draw a CV cable from one of the MOD outputs to your Subtractor Modulation Input of choice.

Envelopes are generally not so easy to use as stand-alone modulators because they need something (usually a MIDI note) to trigger them. Where they do come in handy is overcoming internal modulation restrictions. Let's take Subtractor again as an example. It only has one freely assignable envelope, the Mod Envelope. But what if you'd used this to modulate oscillator FM amount, but still needed a separate envelope to modulate oscillator phase? Answer: commandeer the Filter envelope for the job, via CV. Flip the rack, then draw a cable between the Filter Env CV output and the OSC Phase CV input, within the same instance of Subtractor. You get your second envelope, and it triggers at the right time too!

Here's one last thing before we move on. Thor is the most flexible synth CV source by far. Check out the four generic CV sockets on the rear panel. What are they connected to? You decide, with Thor's modulation matrix. Choose 'CV Out' 1-4 in one of the Dest[ination] slots. Then decide what feeds it from the Source slot. Dragging in the Amount field decides the strength of the effect, positive or negative. Joining the usual synth stuff are performance controllers like Mod Wheel and Breath Control. Weirder by far, though, is audio modulation, from Thor's own oscillators or routed in from elsewhere in Reason via Thor's audio inputs. Check out the Reason workshop from the May 2011 issue of Sound On Sound for more.

Dedicated Sources

The Matrix pattern sequencer speaks only CV. Step sequenced note patterns and modulation shapes are its stock-in-trade.

There are actually two Propellerhead devices dedicated to generating CV signals — and three if you count Rack Extensions.

The Matrix pattern sequencer can generate three simultaneous CV streams, from its 32 onboard patterns. Completely variable 'Curve' CV values are programmed by clicking and dragging in the upper part of the red and black display. Then you can enter step-sequencer style pitch information by flicking the Curve/Keys switch, and clicking in the same area whilst referring to the little keyboard scale to the left, and the five-position octave switch below. At the very bottom is a much shallower Gate row, meant to represent note-on/off triggers. The 'Tie' toggle button, when it's switched on, allows longer note values to be created by entering many notes adjacently.

The RPG8 arpeggiator is another inspiring CV source, and not only for triggering notes.One way to hook up the Matrix is to connect its Note and Gate CV outputs to the matching inputs on most synths; this gives you a monophonic step-sequencing arrangement. Then there's the possibility of controlling a synth parameter with a cable from the Curve CV output too. But in fact those names — Curve, Note, Gate — are completely arbitrary. You can generate largely the same CV shapes or values with any one of them. Also, I frequently use only the Curve output, to make repetitious, envelope-like or quasi-random shapes that modulate synth parameters in a rhythmic way. Need a step-sequenced filter effect? Connect the Curve output to a synth's cutoff frequency CV in, program a jagged pattern, and you're there.

The RPG8 Monophonic Arpeggiator is more of a specialised device; a kind of instrument front-end that processes your MIDI input. When you create one, you get a sequencer track to drive it, but you must also hook it up to another instrument via CV, so it has something to drive itself. You match Gate and Note CV ins and outs as before, and dedicated CV outs for your modulation wheel and pitch bend also tally up with inputs on nearly all instruments. Once you've done this, on the front panel, it's all quite intuitive, like many synth arpeggiators.

Finally there's the Pulsar Rack Extension. This is two LFOs and a simple envelope in a box. If you own it, it's often a less invasive presence in your rack than using the LFOs of a synth for modulation duties. It has some unique features for modifying waveform shape, too. See the August 2012 Reason workshop for an in-depth look.


Check out the rear of Redrum or Kong. Every one of the drum channels of both of these devices has a Gate Out socket (as well as a Gate In). One use for them is to connect a synth or sampler, which is triggered any time the drum plays, for reinforcement or layering.

Run a CV cable from a drum channel's Gate Out socket to the synth's or sampler's (Sequencer Control) Gate In. Now a note will play whenever the drum does, so choose or create an appropriate pitched or noise-based timbre. Also note that only the attack and release phases of the instrument's envelope generators will really do anything.

You can also see how this might lead to using Redrum to program patterns for whole banks of synths (playing appropriately cheesy synth-drum sounds, I hope) with no actual sounds from Redrum itself. Right-clicking an empty part of Redrum's panel and choosing Reset Device will clear the whole device ready for this, or you can right-click a single channel and choose Remove Sample to 'unload' individual sounds.

Only The Beginning

This is only the start of what can be done with CV in Reason. Next month we'll look at some more interesting techniques, and at the astonishing range of third-party CV tools that are being released in the Rack Extension format.  

Tangled Web

All the CV connections we've looked at in this article have been made directly from source to destination. But what if you need one CV source to go to multiple destinations, or to combine two CV signals into one? For this, look to the Spider CV Merger & Splitter. This little half-rack helper can merge four incoming CV streams into one output, and split two signals to four outputs, with the values of one of them inverted.

A good way to explain this is to go back to that auto-pan example in the main text. Let's say you wanted two synth pads to auto-pan in mirror image. Use an LFO CV source and patch it to one of the Spider's Split inputs. Draw a cable from one of the outputs to the PAN CV inputs of the Mix device for the first synth, then another from the INV[erted] output to the other synth's PAN CV input. Bob's your uncle!

Published April 2013

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