Zed Synth User Guide | JazzMan Ltd

Zed Synth User Guide

Note: the app now has had a major face-lift but it works just the same.

Playing Sounds

Zed Synth starts up ready to play with the patch list on the left, and a Perform view next to it.

You can play sounds on the keyboard below. Headphones or loudspeakers are highly recommended to truly hear what the synth is capable of.

The Patch List allows you to quickly find patches: simply click the category you want, then pick the patch.

In the Perform panel you can see the currently selected patch, as well as two graphs. The left & right arrows allow you to cycle through all the patches one by one.

1- Wave-Form: the first graph displays the current wave-form. This may become chaotic if the sound is very complex.

2- Stereo View: the second graph displays the left audio channel plotted against the right audio channel. This sound-field view is frequently used by audio engineers to get a visual representation of a sound. If you see a straight line it means that the left & right channels are perfectly correlated, essentially a mono signal simply panned to the left or right.

Resizing the Keyboard

Scroll to the “Settings” panel and slide the “Keyboard Octaves” knob to a new value. On an iPhone you may be able to play about 2 octaves, on an iPad up to 4. The higher settings are useful for display when you have connected an external controller keyboard.

Processing External Audio

One of the most exciting features of Zed Synth is that you can use it to transform the output of any other synthesizer or drum machine running on your device.

Patches in the Audio category are filters (effects): they process the input audio (microphone or Audiobus) and run it through the Zed Synth’s resonator & effects to radically transform the sound. You really need to use Audiobus to get the most out of these patches, for example routing a drum machine through the Zed Synth to create pitched sounds out of beats.

Here’s an example set-up in Audiobus using Propellerhead’s “Figure” to create a beat and running it through Zed Synth to play it as a pitched musical instrument:


Zed Synth is fully compatible with Audiobus’ preset saving system, so you can save this layout in Audiobus along with all the synth’s settings and restore that session at a later time.

Audiobus is an indispensable tool for serious music making on IOS - click here for more information.

MIDI & External Controllers

To get the most out of the Zed Synth you will really want to connect up an external controller keyboard. Typically this can be done using a USB connector via Apple’s “Camera Connection Kit”. Many IOS compatible controller keyboards are available. A sustain pedal is also recommended if you want to play keyboard sounds (piano etc.) and this can also control Zed Synth’s Spring Box effect which simulates the sympathetic resonance of a piano’s strings. MIDI over Wi-Fi is also supported though this requires some set up.

The MIDI Channel number is configured in the Settings panel. If set to “Omni” the synth will react to messages sent to any channel.

Zed Synth will automatically adjust the BPM setting if it detects a MIDI clock signal from a sequencer or drum machine for example. 

MIDI Learn

You can also use your controller’s knobs & sliders to edit the Zed Synth’s parameters. However you need to teach Zed Synth what the controller numbers are.

- Slide out the Editor panel on the left.

- Select MIDI Learn

- Press & hold a parameter you want to control remotely.

- Adjust the knob or slider on your controller that you want to use.

The MIDI CC number for that controller will appear on the Zed Synth ’s screen and you will see the knob turn and hear the sound change correspondingly.

These settings are automatically saved in your IOS device, independently of the patch used, and will be recalled next time you use the app.

Saving & Sharing patches

If you’ve tweaked a patch or created a completely new patch you’ll want to save it to memory. This is easily done by pressing the Save… button in the Editor slide-out on the left hand side.

- Press Random Name to generate a suitably inspiring wacky name.

- Press Delete to delete an existing patch from memory. (Warning! This can’t be undone, but you can still save the patch again immediately afterwards if you did mess up).

- Press E-Mail to send the patch to a friend or colleague via e-mail. On the receiving end, simply pick ‘Open in Zed Synth’ to add the patch to your collection.



Full context sensitive help is provided throughout the application: simply press the ? sign in the top left of any panel to enable help, then touch any knob or panel name to learn more about it. Press the ? sign again to disable the help pop-ups.

Navigating the Synth

Although you can reach everything by scrolling the screen left & right, this quickly becomes tedious. Fortunately there’s a much faster way of getting around: simply tap on a panel’s heading to jump back to the Synth Overview panel. From there you can tap any other section to jump to that panel. This makes editing much faster.

The Synth Overview panel also shows you how the audio signal is routed through the synth.

Adjusting Knobs

Zed Synth has a few little secrets to make editing much easier:

- Slide your finger up & down over knobs to make large adjustments.

- Slide your finger left & right to make fine adjustments.

- Double-tap to jump to min, half-way and max values.

Creating a blank patch

Slide out the Editor panel on the left and select Init. Patch if you want to start from a fairly blank slate.

The initial patch has a few basic routings built-in:

- Note velocity modulates the Volume & Mallet Amplitude so playing harder results in a louder tone.

- Note Number modulates Pan so low notes play on the left and high notes on the right.

- The Mod Wheel controls the amplitued of the Modulation Evenlope.

- Note Velocity modulates the Filter Envelope Amount so playing louder results in a brighter tone.

- The Filter Envelope modulates the Filter Cut-Off.

All these modulations are very easy to change using the Editor panel on the left.

The Analog Synth

Zed Synth is a hybrid synth: it includes a full classic two-oscillator virtual analog synth with 2 oscillators and a filter section. The amplitude envelope controls the sounds volume over time, the filter envelope modulates the filter cut-off. Two LFOs and an additional modulation envelope can be routed to any parameter. At the end of the signal chain a number of effects are provided to further enrich the sound.

Wave-Shaping Oscillators

Inspired by 1950s vacuum-tube technology, 4 parameters allow you to create a vast array of oscillator shapes which can then be modulated in real-time. Using these parameters you can recreate traditional analog wave-shapes as well as a huge number of other wave-forms.

The Repeat parameter is particularly interesting: it repeats the wave-form a number of times creating an even buzzier sound ideal for creating new bass tones.

A genuine sub-oscillator is available with the same shape as the master oscillator. You can adjust the mix of the sub & master oscillator.

Oscillator 2 can be sync-ed to Oscillator 1 causing the wave to reset each time Osc. 1 resets. This allows you to recreate the classic ‘Sync’ sound of analog synths.

Synth Mixer

This is where the sound from the oscillators is combined to create the output of the analog synth.

Beyond simply mixing the amount of Osc. 1 & Osc. 2, you can also mix in other modules:

- Ring Modulation: classic module multiplying the output of Osc.1 & Osc.2

- Cross Modulation: an innovative module similar to Ring Modulation but with a fuller tone.

- Max 1&2: maximum of Osc. 1 & 2.

- Noise: if positive this just mixes in white noise, but if negative it modulates the signal with noise, a much more gentle effect that better preserves the wave form.

- Ext. Audio: this allows you mix in the microphone or Audiobus input into the signal, a key component to using Zed Synth as an Audio Filter or Effect.


The envelopes are standard ADSR envelopes with a couple of tweaks:

- Every envelope has an Amount or Volume parameter that changes its maximum amount. The Filter & Modulation envelopes can have negative amounts. If the amount is 0 the envelope won’t do anything.

- The envelopes have an additional Slope parameter. If this is zero you have a standard ADSR envelope. But if it’s positive the envelope will increase back to its maximum level, or decrease to 0 if the parameter is negative. This allows you to create sounds that crescendo gently after the intial Attack/Decay phase, or fade away at a different rate than the intial Decay phase.

- The Convexity parameter allows you to change the shape of the envelope slopes, allowing you to more closely replicate natural sounds.

These parameters make it easy to create useful & natural envelopes shapes.


One of Zed Synth’s great features is how easy it is to add modulations:

- Slide out the Editor panel on the left.

- Select the modulation source (Velocity, Note Number, Mod. Wheel etc.)

- Tweak the parameter you want to change.

In this screen shot you can see how the Filter Envelope modulates the the Filter Cut-Off by 4 octaves (48 semi-tones).

Don’t forget to press Normal again when you are done.

Press Clear Mods to reset all modulations for a given source.

The modulation matrix can contain a maxiumum of 30 invidual modulation sources & destinations.

At this time the effects parameters cannot be modulated in this way (a future enhancement maybe!).

The Physical Modelling Synth

Physical modelling is a technology developed in the early 90s, before samplers reasonably had enough memory to record real instruments. It aims to recreate classical instrument sounds through calculating the behaviour of a strings, wind bores, membranes, reeds, mallets and other physical components musical instruments. Whilst this technology can create a vast array of incredibly realistic sounds, the models are very complicated to build and fine-tune, and each model tends to only produce one type of sound. 

Although Zed Synth started out with much a more complex physical model that has now been pared down to a single resonating string which gives a lot of flexibility whilst remaining relatively easy to adjust.

Important: please ensure you adjust the mix of the Resonator in the Final Mix section. If it is 0 the Zed Synth will save CPU and won’t calculate this section at all!

The Resonator

The key component in Zed Synth is the Resonator. This simulates a single string or column of air. It can be excited at a given point by either a mallet striking the string, or a continuous signal bowing or blowing the string.

The point at which the excitation takes place has a big impact on the sound, this is the Position parameter.

The Sustain Time determines how long it takes for the sound to decay following an initial strike.

New! The sustain time can now be infinite.

The amplitude envelope’s Release Time determines the how long it takes for the sound to decay once a key is released.

The Input Amount determines the maximum strength of the signal being inject into the string. This is further modulated by the amplitude envelope, the maximum force exerted on the string is 14.1%. 

This signal can be modulated by virtual analog synth’s output - in the example above the input signal is exactly the synth signal as modulate = 100%.

The Mix Method determines how the incoming signal is mixed with the current state of the string. Different methods are possible to simulate hitting, blowing or bowing the string.

Examples include:

- Blend: simply adds the incoming audio to the resonator.

- Bow Models: simulate the slip/stick response of a string being rubbed by a bow.

- Pressure Models: simulates the effect of blowing (or sucking) a wind instrument.

- Replace: the incoming audio simply overwrites what’s already in the resonator - good for effects.

- Brass: a special model simulating the interaction of the lips or reed with a column of air.

The Mallet

Although it is possible to excite the Resonator using a small pulse of sound generated by the VA Synth section, Zed Synth provides a more sophisticated & dedicated mechanism for doing so: the Mallet.

The Mallet generates an extremely short burst of sound (or displacement) when a key is pressed. It also has a Click-Off amount when the key is released which is useful for replicating the sound of the plectrum on a harpsichord, or keyboard clicks.

The mallet has a width proportional to the period of the note being produced, but can also be configured to be a constant across all notes using the Fixed Width parameter. A width of 0 produces no sound.

The mallet can be modulated by the Analog Synth (which itself can include the Audio Input). This allows you to sample the synth/audio in much the same way granular synthesis would, and can make for interesting patches that periodically sample the input audio and loop it using the Resonator.

Final Mix

This section mixes the output of the Analog Synth and the Resonator, prior to injecting this to the Filter section.

It has a few tricks up its sleeve however: the mixer incorporates a few specially designed pitch-shifters which can help enrich the sound for very little CPU cost:

- Detune: adds two copies of the signal detuned one lower and one higher.

- Sub-Osc: mixes in the signal pitch-shifted one octave lower. At mix=100% you won’t hear the original sound any longer.

- Super-Osc & Pitch: this mixes in the signal pitch-shifted up to two octaves higher.

The pitch-shifting works quite well on periodic wave-forms, with very little artefacts, it is however less bright than a genuine sub-oscillator would be. If you want a genuine detune effect, I’d suggest you take a look at the Unison section, but this will eat a LOT more CPU.

The Filter Section

Zed Synth’s filter section actually comprises two 2-pole filters that can be configured in parallel or in series to obtain various spectra.

Note that the graph in the Filter section doubles as either an oscilloscope or a gain/frequency plot if no sound is playing. Here you can clearly see the twin peaks of a low-pass filter and a high-pass filter added together (in parallel). The cut-off & resonance of the 2nd filter can be controlled & modulated independently of the first where this makes sense.

The Dry/Wet mix is another unusual but very useful feature: it allows you to better emulate vintage synths where the analog filters are not perfect and leak a bit of high frequency sound. Setting the mix at 98% for example allows some of the original signal through and can add interest to a filter sweep.

The Spring Box

This is a uniquely powerful and CPU hungry effect using physical modelling technology. This can be used to process the sound from the Zed Synth’s own oscillators & resonator, or to process external audio via Audiobus.

This effect may have a lot of parameters, but the basic idea is pretty simple: it simulates an array of up to 88 strings vibrating sympathetically with the input signal. Each string has its own low-pass resonant filter, and there is an overall high-pass filter to tame the low-end.

The graph on the right displays the frequency gain chart of the effect, if all the strings are “open” ie: resonating.

The effect can work in two modes:

- Always Ringing: a bit like a spring-reverb, all the strings are open all the time, resonating to the input signal.

- Keyed: like a piano, the strings are only opened when the corresponding key is pressed, or the sustain pedal is pushed down.

- The Low-Pass Filters are adjusted by the relative Cut-Off & Resonance parameters.

- The number & tuning of the strings are adjusted by the Number, Stretch Tuning and Fine Tuning parameters.

 If using this effect in “keyed" mode, to simulate a piano-like instrument for example, you need to set Stretch Tunning to 0 as otherwise the strings won’t correspond to keys. 

In “ringing" mode it can be interesting to place the strings anywhere in the audio spectrum and at whatever spacing you like. This can really create new and interesting sonic atmospheres & backgrounds.

All the parameters are explained in detail through the built-in help system by pressing ?.

Important: this effect may not work fully on older devices will less powerful CPUs, the sound may stutter and Zed Synth will automatically reduce the number of strings till the CPU load is manageable.

Performance Features

Unison Mode

Unison mode allows you to trigger multiple voices when you play a single key. The voices can be slightly detuned, delayed and panned to further enrich the sound.

Enable the Monophonic switch if you want to restrict the synth to playing only one note at at time.

Note that Unison can use up to 7 voices for each key pressed, this can create a huge sound, but it does eat up polyphony & CPU!


This performance-oriented feature makes new notes progressively ‘glide’ to their target pitch as on vintage analog synths. Zed Synth goes one further introducing polyphonic glide allowing you to play several notes at a time and then glide to a new chord. A chromatic Glissando effect is also available, and you can opt to only trigger glide if playing legato, so clearly separated notes jump to their new pitch, but legato notes slur.

Lastly the Legato Envelopes option instructs the synth not to re-trigger envelopes if playing legato. Combined with glide, this can be very helpful to simulate classical solo instruments, slurring between notes except if they’re played distinctly.

The Granulator

A different take on the ubiquitous arpeggiator, the granulator can periodically, or randomly, retrigger the sound, its envelopes or LFOs, and also vary the pitch. This makes it possible to create rhythmic chorded sounds with a human feel to them, or completely chaotic sounds like gentle rain on a windscreen.

Irregular randomises the beat in a chaotic manner.

Humanify plays with the beat but with a random variation either slightly ahead (if negative) or behind (if positive). This results in very natural sounding sounds, particularly if you hold a chord down for example.


The End?

or the beginning of something new!!

That’s it! Well done for reading this far! I really hope you enjoy the Zed Synth and do feel free to drop me a line with comments, suggestions or feedback on the support page. Great reviews on the App Store are always most welcome ;o)

© JazzMan Ltd 2015