Copyright: VAZ Help File v1.0 Copyright © 1996, Martin Fay


Welcome to VAZ

Welcome to the Vurtual Analogue Synth Emulator, or VAZ for short. This program is a real-time model of an analogue synthesizer.

If you have not setup the programs parameters for wave playback see Setting Preferences.

If you are new to analogue synthesis, there is a brief tutorial to explain how the program works.


VAZ Specifications

Signal Path

2 DCO → DCF → DCA

Oscillators

Range: 33Hz to 10kHz

Waveforms: Sawtooth and variable pulse

Frequency modulation: 2 inputs with 1 octave range

Pulse width modulation: 50% to 94%

Other: Oscillator 2 hard sync to oscillator 1

Filter

Response: 12dB/Oct lowpass resonant

Tracking: -50% to +150% of input pitch

Modulation: 2 frequency and 1 resonance modulation inputs

Amplifer

Modulation: 2 amplitude modulation inputs

Other: variable overdrive

LFO

Range: 0.02Hz to 20Hz

Waveforms: Triangle, rising saw and square waves

Envelopes

Response: Exponential

Times: Minimum attack time 4ms

Sequencer

Steps: 1 to 16

Tempo: 1 to 255 bpm

Note range: C-1 to G9

Modifiers: Double step length, rest and variable accent

Control: 2 variable modulation outputs


The Synthesizer Controls

VAZ is layed out with each seperate element, or module, of the synthesizer in it's own box. The audio signal is created by the Oscillators, and then passes through the Filter and Amplifier. Each of the modules is described in turn below:

Digital Oscillator 1

 The oscillators create simple waveforms which are then modified by the other sections of the synth to create interesting sounds. The range control selects the base pitch of the oscillator (the values 32' to 2' refer to the equivalent length a pipe would be to create this pitch). The waveform control selects either a sawtooth or square/pulse wave. The pitch of the oscillator is controlled by the note being played and also by up to 2 modulators, which can be any of the LFO, Envelopes or Sequencer outputs. The pulse width of the pulse wave can also be varied. If the source fixed is selected then the depth control varies the wave from a 50% pulse (or square) wave to a 95% pulse wave.

Digital Oscillator 2

 This is similar to oscillator 1, but with some additional controls. Tuning controls with a range of -12 to +12 semitones and -1 to +1 semitones can be used to detune the 2 oscillators. Sync causes the oscillator to retrigger when saw waveform of oscillator 1 reaches it's peak. Oscillator 2 can also accept oscillator 1 as a modulation source which produces interesting noises to say the least, this is the analogue form of FM (Frequency Modulation) as used by the Yamaha DX series synths.

Digital Filter

 The source mixer controls how much of the output of each oscillator is sent through the filter. The filter is a resonant lowpass type, with the cutoff frequency (above which any sound is filtered out) controlled by the frequency slider and the resonance (the amount sound around the cutoff frequency is emphasized) controlled, predictably, by the resonance slider. Classic 'squelchy' sounds can be made by sweeping the cutoff frequency with a modulator.

 There are 2 modulation inputs for the cutoff frequency and one for the resonance which work similarly to the oscillators modulation controls. Also the cutoff frequency can be made to follow the pitch of the oscillators by raising the pitch follow slider.

Digital Amplifier

 The amplifier controls how loud the sound is. Normally an envelope would be selected as one modulation source which will with the default settings will start a note when key on a controller keyboard is pressed and stop the note when the key is released. The amplifier also has an overdrive controller which adds a distortion effect to the sound.

LFO

 The LFO or low frequency oscillator is used to vary (i.e. modulate) something over time. A classic example of this is vibrato, a slight modulation of the frequency of a sound.

Envelopes 1 & 2

 The envelopes are of the ADSR type. They start at zero, then when triggered by a key press they raise to a maximum value at a rate set by the A (attack) slider, then fall at a rate set by the D (decay) slider to the S (sustain) level. When the key is released the envelope value then drops again to zero at a rate set by the D (decay) slider.

 The inverse envelope selections on the modulation source lists reverse this so the value falls from a maximum to zero etc.

Sequencer

 The sequencer button show the sequencer window which is described on a separate page.


The Sequencer Controls

The VAZ sequencer is modelled along the lines of the sequencer section of the Roland TB303, with some extra controls on top. The sequencer has 16 rows for each parameter.

Note

 The note to be played for this step.

D (Double)

 Doubles the length of this step.

R (Rest)

 Silences this step: a note is not played.

S (Slide)

 Slides from this step to the next one, the note continues without a break and it's pitch changes to meet the new note.

A (Accent)

 If the accent is checked for a step then the Accent modulation value found in the modulation source lists is set to the value set by the Accent Level slider in the Master Controls section. If Accent isn't set then the Accent modulation value is zero.

Modulation Outputs

 The values set here are sent each step to any modulation inputs on the synth which have selected Sequencer 1 or 2 as an input.

Master Controls

 The sequencer is started and stopped here, the tempo can be set and the step at which the sequencer loops is set.


Setting Preferences

The Preferences dialog is used to choose settings for wave playback and midi input.

Wave Output Settings

 Wave Output Device will normally be set to "Automatic Selection" unless you have several soundcards and VAZ chooses the wrong one!

 Sample Rate defaults to 11kHz which even a 486SX/25 might just manage to cope with. A 486/66 is just about capable of 44kHz playback, but the UI may become unusably sluggish.

 Wave Buffer Size and Queue Length can be tweaked to taste until the playback does not stutter. Optimal settings will be different from system to system, but the total (size * queue) needs to increase with the sample rate. My machine works well at 22kHz with 7 * 1k buffers.

 Note that Windows 95 has a bad habit of stealing the processor from time to time. Especially when the Plus Pack is installed, so the occasional bout of stuttering may be unavoidable.

MIDI Settings

 If you have a MIDI keyboard connected to your computer you can use it to play VAZ. Just select the interface it's connected to from the pop-down list.

 There is a delay of around 0.3 seconds after a key is struck before VAZ plays. This is due to the windows wave-playback system, but a future version may be able to improve this problem by using DirectX.


Capturing Sounds

To capture (i.e. record) sound to a wave file, select File|Capture and then set a file to record to in the dialog that appears. When OK is pressed in this dialog VAZ starts recording. To stop recording select the File|Stop Capture menu item that is now visible.

If VAZ stutters more when recording to file because of the increased system load, don't worry because the stutters don't get recorded!


Lesson 1: Emulating the TB303

This step-by-step lesson assumes no knowledge of VAZ or synthesis in general, and guides you through every step of creating a sound along the lines of a Roland TB303 Bassline.

Step 0

 If you've changed the controls from the startup defaults, then either restart the program or return them to the default positions.

Step 1

 First we will program a simple phrase into the sequencer so the program can make some noise. Press the "Sequencer" button at the bottom of the second column to show the sequencer window.

Step 2

 Click on the pop-down button of the top note combobox, and select C5. Select G4 for the 4th step.

Step 3

 Check the S (slide) column for row 1.

Step 4

 Use the spin control to reduce the "loop at step" value to 4, so only the first 3 steps will be played, and the hit Start. You will hear the pitch slide down from step 1 to step 2. Press Synthesizer Controls to return to the main window.

Step 5

 At the moment you can hear a plain sawtooth wave. Click the Pulse radio button in the Digital Oscillator 1 box to hear a square wave, and then Saw to return to a sawtooth.

Step 6

 We will now filter the sound to make it more interesting. Move the frequency slider of the Digital Filter slowly down to about a half, and listen to the high frequencies become removed from the sound.

Step 7

 The resonance control emphasizes frequencies at the cutoff point of the filter. Raise the resonance control slowly to about 3 quarters. Now raise the frequency control slowly to full and back to a half to hear the emphasized frequency move.

Step 8

 Now we'll add some interest to the sound using modulation. The first filter Frequency Modulation source is a combobox about half way down the filter panel. Pop the list down and select Envelope 2 as the source. Now move the depth slider below to about an eighth of the way up. You'll notice that the filter cutoff rises, but nothing interesting happens yet.

Step 9

 The envelope as it is set raises to a maximum value very quickly and hold  there until the note ends. Reduce the level of the envelope 2 S (sustain)  slider gradually to zero. You'll hear a short blip at beginning of the note  where the envelope briefly (very!) opens. Raise the D (decay) slider to 3  quarters and the envelope value will drop more slowly. You'll now hear the  filter sweep down as each note is played.

Step 10

 Finally, raise the Overdrive slider in the amplifier box to about 3 quarters to add some bite to the sound. Now have a play around with all the sliders we have used to see how it affects the sound!

 It is possible to get even closer to a 303 sound using the accent feature of the sequencer, and careful modulation, but it would be too long-winded to go into here.

Lesson 2.


Lesson 2: Your Friend the Oscillator

After Lesson 1 you should have a basic understanding of a lowpass resonant filter, and using an envelope to apply modulation. This lesson examines what can be done using 2 oscillators as opposed to 1.

Step 0

 If you have just done the first lesson, then either restart the program or reset the controls to the startup defaults. For this lesson you can either audition sounds using a MIDI keyboard (see Setting Preferences for how to do this), or by setting the sequencer to play slowly at, say, 30bpm.

Step 1

 A 2 oscillator synth is able to create much "thicker" sounds than a single oscillator machine. One simple trick is to use 2 oscillators set to fractionally different pitches, or detuned. Move the Source Mixer slider at the top of the filter panel to the middle of it's range so you can hear both oscillators. Actually, you won't hear any difference. This is because the oscillators are exactly in tune and phase at startup. Move the -1 to +1 tuning slider in the oscillator 2 section by a small amount to detune the oscillators. The sound should now vary in a subtle way.

Step 2

 Larger changes in tuning can also have interesting effects. Change the top slider in the oscillator 2 section to different positions to move the pitch of the oscillator up and down in octave intervals. Return the slider to 8' when you are done. The -12 to +12 slider moves the pitch in semitone intervals. If you click the right arrow button 7 times you will raise the pitch of oscillator 2 by a fifth which is a useful tuning.

Step 3

 Now set the Source Mixer control to Osc 2, and check the Sync checkbox to the right of the waveform selection controls in the oscillator 2 panel. You'll notice that the pitch of oscillator 2 drops to match oscillator 1. What Sync is doing is restarting the oscillator every time oscillator 1 finishes a cycle. This can produce rich, interesting sounds. Switch oscillator 2 to 4' to hear a more extreme effect. If you have a MIDI keyboard attached then you can play 2 notes at once to control each oscillator independently and hear the variation of sync sounds.

Step 4

 Sounds can be made much more interesting if modulatiom is used to vary them with time. Select the first Frequency Modulation source for oscillator 2 to be Envelope 2, and turn the depth control fully up. Now turn the decay (D) of envelope 2 to about 3 quarters and the sustain (S) fully down. The sound you now have is called a "sync sweep".

Step 5

 Finally, something over the top! Change the Frequency Modulation source to DCO1 (the output of oscillator 1), and set oscillator 1 to 16' and oscillator 2 to 2'. You should now hear a strange harsh sound. What you are doing here is called FM (i.e. Frequency Modulation), but analog style with complex waveforms instead of sinewaves as Yamaha DX synths.

Step 6

 This lesson should have shown you that it is possible to make interesting sounds without even using the filter. Try combining this lesson with the last and see what you come up with!


VAZ Plus

It is intended to add extra features to VAZ, which will then be sold for a small fee. Possible features include:

•	Patch and pattern memories, which can be saved to file.

•	More filter modes including 12/18/24 dB/Oct lowpass resonant and highpass are possibilities.

•	A polyphony option for faster machines, so chords can be played.

•	DirectX support to reduce latency, which currently means notes played on a MIDI keyboard are delayed by around 300ms.

•	Expanded help file, with full synthesis tutorial.


VAZ Pro

This will be a longer term development and will be a full modular design, where modules can be created as they are needed and patched together however you like. There will be various new modules including a ring modulator and a sample based  oscillator.


Keeping up with VAZ

There is a VAZ web page at http://www.cp.umist.ac.uk/users/martin/vaz.html which will be kept to up to date as VAZ develops.


Background to Synthesis

Briefly, I have a fascination with analogue synths, but as yet I have no practical experience with electronics. However, I can write code! Hence the decision to write a virtual synth program. The design steals mainly from 2 synths, the ARP Odyssey (I'm lucky enough to possess one) which influenced my decision to include cross-modulation between the oscillators and the quite extensive modulation possibilities, and the Roland TB303 which accounts for the sequencer design and also some tweaks such as resonance modulation and overdrive to improve the impression of a 303 VAZ can manage.


Bug Reports and Suggestions

Bug reports and suggestions can be sent to martin.fay@umist.ac.uk.

I would be very happy to receive comments on the controls available, any you think would be highly useful to add, and the ranges of the controls present. This has been set pretty much by "feel" at the moment, so I'm sure there are likely to be 1 or 2 places the range I've selected isn't too sensible!


About the Author

Martin Fay

martin.fay@umist.ac.uk


License and Conditions

This software is licensed for evaluation purposes only. In particular, no sounds created using this software may used in any musical composition which is publically released, without the prior consent of Martin Fay.

No Warranty

Martin Fay provides absolutely no warranty. The software and information are provided "as is" without warranty of any kind, either express or implied, including, but not limited to, any implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the quality and usefulness of the software and information is with you. Should the information prove to be incorrect and/or software not work as expected, you assume the cost of all necessary servicing, repair or correction.

In no event will Martin Fay be liable to you for any damages, any lost profits, lost monies, or other special, incidental or consequential damages arising out of the use or inability to use this software and/or information (including but not limited to loss of data or data being rendered inaccurate or losses sustained by third parties), even if you have advised us of the possibility of such damages, or for any claim by any other party.