Building a Synth - Computer Music Tutorials, updated for Reaktor v4.

The originial versions of these tutorials are available at the Computer Music Magazine website

Reaktor Tutorial : Introduction

This tutorial will show you how to build a simple synthesiser in Reaktor 4, step by step. It was written for Reaktor 4, but with Reaktor 5 the construction principles are pretty much the same. This tutorial is compiled from two other tutorials: Jake Mandell's introductory tutorial (on the Native Instruments homepage) along with the Reaktor 2 tutorial from Computer Music Magazine (updated for Reaktor 4).

Reaktor terminology

Before we can get our hands dirty building something, it's important to understand a few basic things about Reaktor:

Module: A module is the most basic classic Reaktor building block (update: REAKTOR 5 has introduced lower levels, the so-called Core Structure, allowing you to construct custom-made modules).
Some of the classic modules are really elementary, such as a simple adder or multiplier. Other modules are quite complex, such an event table that can be used to store or sequence information. Some modules make sound, like the oscillators and time-stretching samplers. The modules also include a wide range of filters, and several sorts of delays, distortions, shapers, and more. You can’t look in the structure of the modules, but you can change their properties when appropriate. For instance, you can adjust the maximum delay time on the delay modules, or the size of the event tables. Even user-interface elements, such as knobs, faders, menus, and level meters, are elementary modules.

Macro: A macro is an encapsulation of modules or other macros. Macros form the heart of Reaktor’s hierarchical structure. There’s no limit to how many macros you can have stacked inside each other, nor to the complexity of a single macro. Macros make it easy to build up complex instruments from pre-built parts. We’ll primarily use macros when building our example synth. It’s possible to contain an entire oscillator or filter section within a macro, for instance.

Instrument: An instrument is something that you can play. Examples of instruments include a synthesizer, sampler, delay effect, sequencer, drum machine, etc. An instrument can contain modules, macros, or even other instruments. Reaktor lets you easily set the polyphony of each instrument, from one up to 1024 voices! Each instrument can respond on a certain MIDI channel, so you can set up complete multitimbral arrangements within Reaktor. You can store snapshots with an instrument. A snapshot is a patch or preset or a setting or a sound or whatever else you want to call it. Each instrument can have multiple banks of 128 snapshots, and Reaktor lets you randomize and even morph between different snapshots.

Ensemble: Ensemble:The ensemble is the highest-level structure in Reaktor. You can only connect instruments together at the ensemble level. Ensembles also have snapshots however, and when you recall an ensemble-level snapshot, then all the instruments contained in that ensemble will automatically switch to the correct settings.

Constructing a Modular 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...

1. Start up Reaktor, click on File and choose New Ensemble from the drop-down menu. Right click on the Instrument in the centre and look at its Properties… there you’ll find an explanation of what it is (you may need to click on the “i” pane). Break the feedback loop by deleting the two input connections (if you haven’t already).


2. Right click on the Instrument again but this time choose Structure.


3. Select the two inputs and their connectors and press Delete, to leave you with an empty instrument.


4. 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 Insert Module/LFO, Envelope/ADSR from the menus.


5. Now you need to create the controls for the envelope. Right-clicking on the A of the envelope brings up the option to create a control; clicking this to create a controller attached to the input A. You need do the same for the Decay, Sustain and Release.


6. You now need to set how much a control's movement will affect the envelope. Right-clicking on a control calls up its properties (you may need to click on the “tools” pane); leave sustain as it is and change the others' control ranges to 74 Max and 10 Min with a Stepsize of 0.5, then click on the “eye” tab, select the Small and Vertical Fader buttons and close the Properties box.


7. 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 go to Insert Module/Midi In to create Gate, Pitchbend and Notepitch MIDI events.


8. At this stage, your synth should look like this:


9. 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, go Insert Module/Oscillator and select a Sawtooth, a Sine, two Pulse waves and a Parabol wave.


10. Wire the output of the envelope generator into the Amplitude 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 Width of a Pulse oscillator and then delete the connecting wire.


11. The oscillators still have no way of identifying the pitch of the note, or the Pitchbend. You need to 'add' these two 'events' together before connecting them to the Pitch input of two oscillators. Choose Insert Module/Math from the menu, select Add and connect them.


12. You'll want to be able to adjust the tuning between some of the oscillators, so you'll need to create a 3 Event Adder. Use Copy and Paste to create a second 2 event adder, right-click on it, select Properties and switch to the “tools” pane if necessary. Change “MIN NUM PORT GROUPS” to 3.


13. Create controls by right-clicking on tle inputs and, using the Properties box again, name one 'Fine' with ranges of 0.64 max and 0 min, and stepsize 0.005, and just name the second 'Interval'.


14. 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 3 Event Adder to the Pitch input of the two remaining (Pulse and Sawtooth) oscillators.


You need to create controllers for the LFO. Using your Parabol wave as the source, you need to create controls by right-clicking on its inputs. Rename Pitch to LFO and set its range to -70 min, 0 max, with 1 Stepsize, and Ampl just needs renaming to Depth.


16. 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 a 2 Event Adder. Call it up from Insert Modules/Math list and use it to replace the LFO to Pitch connector.


17. 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 Insert Module/Math/Multiply and wire it up as shown. Now right-click the other connector and create a Constant. Use the Properties box to give your constant a value of 0.2. Make sure it’s the value you change, and not just the label. If you give it a higher value than this, the LFO will become too ‘grainy’.


18. Now you need to connect the Parabol LFO to the Width controls of the Pulse oscillators, so create two more 2 Event Adders.


19. 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 as yet unused P-Width controller to both 2 Event Adders. Don’t forget to connect the output of the Adders to the Width inputs of the two Pulse oscillators. The connections you need are highlighted in the picture below:


20. 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. Go Insert Modules/Math/ and select Invert, -x.


21. Connect the LFO (Parabol oscillator) output into the inverter, then into the Audio Adder, though to the Width input of the second Pulse oscillator. Now all you need is a filter to sweep it all, and a few other small additions.



Constructing a Modular Synth, Part 2

For the second, 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...

22. 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 Insert Modules/Panel/Switch.


23. You need to create four switches (one for each oscillator). Wire each switch to each of the four oscillators, and then right-click on the first switch in turn to call up the Properties box. Rename the switch appropriately and then, without closing the Properties box, click on the next switch. You’ll see the Properties box change. Rename the other switches. You might also like to rename one of the Pulse oscillators.


24. 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 Insert Modules/Panel/Level Meter. Create one for each oscillator.


25. 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.


26. 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 Insert Module/Filter/Multi-2 Pole FM.


27. You'll need to 'join' the outputs of the four oscillators into one signal, as the filter only has one input. Look back to step 12 and create a 4 Event Adder. Place the newly created 4 Event Adder in between the filter and the oscillator switches you created earlier. Wire the output of each switch into each of Adder's inputs and then wire the Adder's output to the input of the two-pole filter.


28. 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, as the other inputs are going to be controlled by the envelope we created in steps 4-6. Therefore, just create a resonance control.


29. 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 Insert Modules/Math and select Multiply from the menu.


30. Right-click on one of the inputs of the newly created 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.


31. Connect the output of the ADSR envelope to the other input of the Multiply, and then connect its 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.


32. 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 Insert Module/Math/Add from the menu and create one control for it. Name this control it 'Cutoff', with values of 75 max, -10 min and stepsize of 1.


33. 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 you need to associate it with the Notepitch and Pitchbend events. Connect the sum of these two MIDI events to the 3 Event Adder you created in step 12.


34. This gives the two oscillators (Sawtooth and Pulse) that are connected by the 3 Event Adder Notepitch and Pitchbend compatibility, and by connecting the output of this 3 Event Adder to the input of your recently created Cutoff event, it also gives the Cutoff a pitch to work with.


35. 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 Insert Module/Panel/Switch.


36. In the Switch’s Properties box, change MIN NUM PORT GROUPS to 3 name the switch ‘Filter’. Each of these inputs will need naming, so that you'll know which switch to use for which filter effect in the instruments panel, so Right-click on each, choose Rename Port and name each by its wired counterpart.


37. All that's left to finish off the instrument is to connect the output of the filter to the outputs of the instrument.


38. Close the Instruments window and open the Instrument’s Control Panel in the Ensemble – Panel window. Click to the right of the Instrument label (the icon changes to a spanner). Now organise it so you are comfortable with its layout. Right-click in the Ensemble - Structure window to bring up the effects.


39. Choose any effect you want to use - here it's a fat chorus. Adjust the wiring so that your Instrument signal passes through your chosen effect. That’s it. Now you need to change things around, better to understand how it all works.