Reaktor - Building a Synth

Tutorial - Reaktor - Building a synth part 1

Reaktor may have won the 1999 readers' award for Best Soft Synth but, judging from the amount of mail we get, it's clear that a lot of you still see it as a bit enigmatic when it comes to building synths of your own from scratch. So, being the nice chaps that we are, we've digested, regurgitated, translated and rearranged the manual into something a little more coherent. In this two-part tutorial, we'll be concentrating on building a fairly basic analogue synth that can be used for lead and bass sounds, but more specifically for slow filter-sweeping pads.

The key to using Reaktor is not to get carried away with it; it's all too tempting to stack up 20 oscillators, add a copious amount of controls and expect to have a huge sound. This will most probably end in a noise that swamps the rest of your instruments, and uses up a hell of a lot of your processing power at the same time. The sounds that can be had from Reaktor are determined mostly by which oscillators you're using. Triangle adds a metallic 'ting' (in the same way as the triangle instrument), Sine is basically a whistle, Pulse (also known as square wave) adds a woody, hollow sound (perfect for pads), and Sawtooth is for 'raspy' type sounds. The TB-303 is a good example, having both square and sawtooth waves. There are a lot more oscillators on offer, but it's best to experiment and decide for yourself which will create the sounds you're after.

The number of oscillators you use also affects the amount of control that you have. Too many oscillators can leave you lost in a forest of controls (with the movement of each affecting all the others), but too few and you're left out in the cold. So, put out the cat, lock yourself away, boot up Reaktor and we'll get started...

Constructing a Modular Synth - Part 1Find part 2 here

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Start up Reaktor, click on File and choose New Ensemble from the drop-down menu. First you need

to create an empty instrument to build the synth in, so right-click anywhere in the Ensemble Structure window and select Instruments/New/Out1 from the menu.

Now you've got the instrument, you have to build the circuit board inside to generate the sounds. Right-

clicking on it presents a menu from where you can display its front panel or edit the structure. Choose Structure from the drop-down menu to open up the Structure window.

Expand the Structure screen to full size because there's quite a bit to fit into it. For starters, you need

an envelope for the oscillators so you can control the Attack, Decay, Sustain and Release. Right-click and select Module/LFO, Envelope/ADSR from the menus.

Now you need to create the controls for the envelope. Right-clicking on the A of the envelope brings up the

option of creating a control; clicking again will create a controller attached to the input A. You need do the same for the D(ecay), S(ustain) and R(elease).

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You now need to set how much a control's movement will affect the envelope. Right-clicking on a control

calls up the properties; leave sustain as it is and change the others' control ranges to 74 Max and 10 Min with a Stepsize of 0.5, then highlight Fader and click OK.

The synth has to 'know' when a key is being pressed, so you'll need to connect a gate, but you also want it

to know which key is being played and to understand any pitchbend commands. Call up the menus and create Gate, Pitchbend and Notepitch MIDI events.

Constructing a Modular Synth - Part 1 - Steps 7 - 12
















Now you need to 'wire' the gate into the envelope generator and move Notepitch and Pitchbend out of

the way while you choose your oscillators. Right-click anywhere in the Structure field and select a Sawtooth, a Sine, two Pulse waves and a Parabol wave.

Wire the output of the envelope generator into the (A) input of only four of the oscillators. The Parabol wave

is going to be used as the LFO source to add a 'wobble' effect. Create a control for the W(idth) of a pulse and then delete the connecting wire.

The oscillators still have no way of identifying the pitch of the note, or the Pitchbend. You have to 'add'

these two 'events' together before connecting them to the P(itch) input of two oscillators. Choose Modules/ +,-,X,/ from the menu, select Event Add 2 then connect them.

You'll want to be able to adjust the tuning between some of the oscillators, so you'll need to use Event

Add 3. Create controls by right-clicking on the inputs and name one 'Fine' with ranges of 0.640 max and 0 min, and stepsize 0.005, and just name the second 'Interval'.







Choosing a low range for Fine and keeping the Interval at a large range gives you plenty of control

for detuning the two remaining oscillators. Now connect the output of the Event Add 3 to the P(itch) input of the two remaining Pulse and Sawtooth oscillators.

You need to give control over the LFO. Using a Parabol wave as the source, you need to create controls by

right-clicking on the inputs. Pitch is renamed as LFO and has ranges of 0 max, -70 min with 1 stepsize, and Ampl just needs renaming as Depth.

















The LFO also needs to identify with notepitch and pitchbend, so it works at the same frequency as the

note being played. Again, LFO is an event, so you need to use Event Add 2. Call it up from the modules list and 'bridge' the LFO to Pitch input with the Event Add.

You'll need to multiply the Pitchbend controlling the LFO with a constant event value, so the LFO will stay

at a constant rate with Pitchbend. Call up Multiply Event 2 from the Modules menu, wire it up as shown and create a Constant from the Modules menu to connect up.

Right-click on the Constant and open up the Properties box. Give it a value of 0.2 - higher than

this and the LFO will become too 'grainy'. Now you need to connect the Parabol LFO to the pulse width control and oscillators, so create two Audio +2 events

The Pulse Width control controls the 'width' of the oscillations (giving a more hollow sound), but it's also

controlled with the LFO. Wire the output of the LFO Parabol wave into the top audio connector, and then wire up the Pulse Width controller to both Audio +2 events.







You don't want the same LFO effect on both pulse waves - they'd cancel each other out - so you'll need

to use an audio inverter. This will reverse the LFO signal to the second pulse wave, causing them to 'beat' against each other. Select Audio Invert from the Modules/+,-,x,/.

Connect the LFO output into the inverter, then into the Audio Add event, though to the W(idth) input of

the second Pulse oscillator. Now all you need is a filter to sweep it all, but that, along with a few other additions, will have to wait until next month for...

Back to the IntroYou can Find part 2 here
















For the concluding part of this tutorial on synth building, we'll be concentrating on adding a filter to sweep the sound, as well as a few more controls and switches for a more tweakable, 'hands on' experience.

After oscillators, filters are the next most important feature in a synth designer's sonic arsenal. When it comes to creating and editing sounds, it's vitally important that you offer as much control as possible over them. A separate envelope can be used to control the filter, but in this example we're going to be using the same envelope that controls the oscillators, as this will allow the filter to change with any movements of the envelope's controls, preventing it from drifting out of sync.

Effects also play an important part in how the finished synth will sound. In the example on the following pages we've used a stereo phaser, but it's worthwhile experimenting with all the other effects Reaktor has to offer.

Although there are no hard and fast rules to follow when you are building a synth, it is important to follow a basic structure. Once you understand this basic structure, building more complex synths will soon become second nature, and the beauty of Reaktor is that, if you're not happy with the results, you can just wipe the slate clean without it costing a fortune in solder and parts. You can, therefore, be as adventurous as you like.

Try using different oscillators in place of the ones we're using here, or different filter combinations. Remember: it's your synth and it's there to be used and abused. You'll only get out of it what you put into it - a bit like a relationship really...

So take the phone off the hook, settle down in front of your machine and we shall begin...

Constructing a Modular Synth - Part 2



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We'll start by adding switches to the four oscillators from last month, so when you design sounds on your

new synth you can choose which oscillators you want to use to create a sound. Right-click anywhere in the structure and choose Modules/Panel/Audio Switch 1.

You need to create four switches (one for each oscillator). Wire each switch to each of the four

oscillators, and then right-click on each switch in turn to call up the properties box. Now give each of the switches the same name as the oscillator it's wired to.

To make sure each oscillator is giving a signal, attach a level meter so that when using the Instrument

Control Panel, you immediately see which you're using to make the sound. Right-click and select Modules/Panel/Level Meter. Create one for each oscillator.

Place the level lamps under each of the four switches you created earlier and connect the output of the

oscillators to the inputs of each of the level lamps. Right-click on each level lamp to call up its properties and name each one after its associated oscillator.







Now it's time to add a filter to the synth. In this example it's a multi two-pole FM filter. This offers

Highpass, Bandpass and Lowpass control, giving plenty of filter control over the final sound of the synth. Right-click and select Modules/Filter/Multi 2 Pole FM.

You'll have to 'join' the outputs of the four oscillators into one signal, as the filter only has one input. As the

signal is now an audio signal, you need to use Audio Add to join the four together. Right-click and select Modules/+,-,X,/ and select Audio Add 4.

















Place the newly created Audio Add 4 in between the filter and the oscillator switches you created earlier.

Wire the output of each switch into each of Audio Add 4's inputs and then wire the Audio Add's output to the input of the two-pole filter.

You need a way of controlling the filter. Right-clicking on any input of the filter will allow you to create a

control, but only a resonance control is needed so far, as the other inputs are going to be controlled by the original envelope. Therefore, just create a resonance control.

As the synth's filter is going to be controlled with the same envelope which controls the oscillators, you

need to be able to control how much this envelope will affect the filter. Right-click and select Modules/+,-,X,/ and select Audio Multiply 2 from the menu.

Right-click on one of the inputs of the newly created Audio Multiply and create a control. Right-click on this

new control to access the Properties box, then name it 'Env' and give it a max value 0f 3000, a min of 0 and a stepsize of 20.







Connect the output of the envelope to the 'spare' input of the Audio Multiply, and then connect the

combined output to the filter input of the two-pole filter. The reason for this is that the filter will sweep in time with the oscillators as both are controlled by the same envelope.

There's still no control over the amount of frequencies that can get through, so you'll need to create a filter

cutoff knob. Select Event Add 2 from the menu and create one control from it. Name it 'Cutoff', with values of 75 max, -10 min and stepsize of 1.

















The cutoff must be able to detect which note on the keyboard is being played for it to work effectively and

sweep the correct frequencies, so associate it to the Notepitch and Pitchbend events. Connect these two MIDI events to the Event Add 3 you created last month.

This gives the two oscillators (Saw and Pulse) that are connected by the Event Add 3 Notepitch and

Pitchbend compatibility, and by connecting the output of this Event Add 3 to the input of your recently created Cutoff event, it also gives the cutoff a pitch to work with.

Connect the output of the Cutoff events to the Pitch input of the filter to complete the filters circuit. The

filter has three outputs - Highpass, Bandpass and Lowpass - and you'll want to be able to switch between the three, so call up the menu and select Audio Switch 3.

Each input of the switch will need naming, so in the instruments panel you'll know which switch to use for

which filter effect. Right-click on the switches input to call up the Properties box and name each by its wired counterpart. Now name the switch 'Filter'.







All that's left is to connect the output of the filter to the out of the instrument. Close the Instruments

window and open the Instruments Control Panel. Organise it so you are comfortable with its layout. Right-click in the ensemble window to bring up the effects.

Choose any effect you want to use - here it's stereo flange with a chorus setting. The instrument settings

shown will create a slow filtered pad when played around C1, but it's best to just play around with the controls until you come up with your own sounds.

Back to the Intro















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Reaktor - Building a Synth