Comparison

Zeeon synth vs ButterSynth

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Zeeon synth

This app is a virtual analog synthesizer that recreates the sound and feel of classic hardware. It features a detailed circuit-modeling engine, powerful modulation, and multiple filter models for rich, organic soundscapes. Explore a vast array of presets and expand your sonic palette with additional sound banks.

Highlights
  • Circuit-modeling engine
  • Powerful modulation matrix
  • Dual oscillators with variable waveforms
  • Multiple filter models
  • Built-in effects unit
  • Audio Unit v3 support
  • Polyphonic step sequencer
Features
Read full description

Zeeon is a virtual-analog synthesizer built on a deeply detailed circuit-modeling engine. We’ve studied classic and modern analog synths to uncover what gives them their unmistakable character and recreated that essence with precision. The result is a unique instrument that delivers the warmth, movement, and organic depth of true hardware. While many emulations sound flat, Zeeon breathes. Every note is alive, with tight lows and shimmering highs. All audio and modulation are processed at 176 kHz (4× oversampling) for uncompromised quality across the entire spectrum. “Desktop-class sound engine … fidelity of this analog emulation goes beyond everything else on iOS.” – App Store review Features • Audio Unit v3 and standalone application with a simple polyphonic step sequencer • Powerful modulation matrix offering self-modulation and cross-layer modulation, 8 modulation slots, 17 signal sources and 41 targets available, both from modulation modules and audio signal path. This takes Zeeon into semi-modular territory. Imagine oscillator waveform, panning, filter cutoff, resonance or LP-HP mode modulated by oscillators or another layer! • 2 oscillators with continuously variable waveforms, hard-sync and sub-oscillator. Carefully simulated analog drift and PSU influence. • Filter: 3 models available: Transistor ladder low pass, OTA cascade low pass and State Variable Filter with continuously variable LP-HP + BP mode. • 2 low frequency oscillators and envelope generators per voice. • Overdrive: diode clipper, transistor saturation, wave folder, pre and post filter. • Up to 2 layers per voice. Layers can modulate each other. • Effects unit: Circuit modelled BBD chorus, bass booster, zero-delay Phaser, Stereo delay and Reverb. • 280 presets and Tutorials bank. 3 additional banks available as IAPs. Full manual and audio demos available at the BeepStreet website.

About

ButterSynth

This powerful synthesizer app offers a hybrid approach, combining wavetable, FM, and sample-based synthesis. Create unique sounds with a vast sonic range, advanced modulation, and a built-in effects rack. It caters to both experienced sound designers and beginners with extensive presets.

Highlights
  • Hybrid 6-oscillator synthesis (wavetable, FM, sample)
  • Built-in wavetable editor
  • FM engine with 4 operators
  • Sample and Granulator engines
  • 32-slot modulation matrix
  • Internal FX rack with 16 modules
  • Extensive preset library
Features
Read full description

ButterSynth is a hybrid 6-oscillator wavetable/FM/sample-based AUV3 and standalone synthesizer with a vast sonic range, from gentle pads to screaming leads and basslines. Mix any combination of wavetable, FM, sample and other synthesis engines for one truly massive sound. For the more advanced users, you'll love using ButterSynth's thoughtfully designed interface, incredibly powerful modulation matrix, fully-featured internal FX rack, factory waveform and sample libraries, and almost limitless scope for fun, experimentation and sound design. For less experienced synth programmers, ButterSynth includes a library of hundreds of ready-to-use presets, sparking your creativity to start making music right away. Headline features include - Mix and match any combination of 6 synthesis engines to either emulate your favourite synths of yester-year or build a synth ready for the future. - Dual-wavetable engines also feature 9 phase modes, wave folding, and deep unison controls modelled on vintage hardware synths. - Built-in wavetable editor gives you the ability to tweak, morph, and hand-draw your own custom wavetables, with each wavetable supporting up to 256 frames. - FM engine offers 4 operators with a selection of 12 modulation paths. Each operator can be loaded with any waveform from the factory or user library, and can also self-modulate via the feedback dial. - Sample and Granulator engines both let you load samples (either imported or from the factory library) and control precisely how they are chopped, triggered and layered. Both also feature the same powerful unison modes available in the WT engine. - Highly configurable 32-slot modulation matrix featuring precise mix/max ranges, self-modulation (via the amount target), plus configurable response curves and layer modes. Simply long-tap any parameter to set it as a Mod destination! - Full suite of versatile control sources which includes: 4x MSEG-style looping curve envelopes, 4x LFOs, 4x step sequencers, X/Y pad with motion recording, 8x Macro dials and a powerful arpeggiator inspired by Kirnu Interactive’s Cream. - The EFX rack lets you build your own insert effects chain using any combination of the 16 built-in FX modules. Modules available at launch include delay, reverb, distortion, chorus, OTT compression etc. Note - FX parameters can also be targeted by the mod matrix, unlocking the possibility to program ‘per voice’ modulated effects. - All presets, wavetables, samples and other settings are stored in the Files app, making bulk import/export, backup and community sharing quick and easy. - All of this is housed in an irresistibly designed 4-tab UI that makes synth programming quick and fun.

Screenshots

Zeeon synth3 screens
ButterSynth4 screens

Verdict

The call

The clearest difference is rating: Zeeon synth at 4.8 against ButterSynth's 4.0. Zeeon synth also leads on price ($14.99 vs $19.99) and review sentiment (76% vs 59%). ButterSynth's advantage is in-app purchases (none vs 3). On update cadence, ads, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Zeeon synth costs $14.99 and ButterSynth $19.99 up front. Zeeon synth sells 3 one-off in-app purchases. ButterSynth asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Zeeon synth holds the better App Store score, 4.8 against 4.0. Both are backed by a comparable volume of ratings — 209 and 63 respectively. Written reviews point the same way: 76% of Zeeon synth's written reviews are positive against 59% of ButterSynth's.

UpkeepUpdate frequency

Both ship on a similar rhythm, roughly every 2 months. The most recent releases landed on October 20, 2026 and October 21, 2026 respectively.

Scorecard6 real differences · 4 level
Zeeon synth versus ButterSynth: the parameters behind the verdict, then further details
ParameterZeeon synthButterSynth
Price$14.99 — better$19.99
Rating4.8 (209 ratings) — better4.0 (63 ratings)
Positive reviews76.0% of reviews — better59.2% of reviews
Number of ratings209 — better63
Update frequencyEvery 2 monthsEvery 2 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases — betterPaid
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.614.0 — better
Further details — not scored
Size27 MB468 MB
Age rating4+4+
DeveloperBeepStreetArto Vaarala

Customer experience

Zeeon synth

All ratings209 ratings
Positive93.8%
Neutral2.4%
Negative3.8%
Written reviews167 reviews
Positive76.0%
Neutral7.2%
Negative16.8%

ButterSynth

All ratings63 ratings
Positive73.0%
Neutral7.9%
Negative19.0%
Written reviews71 reviews
Positive59.2%
Neutral11.3%
Negative29.6%

User reviews

Zeeon synth

From 209 App Store ratings

What we love

  • 🎨 Excellent sound quality
  • 🎹 Intuitive and well-designed interface
  • 🔧 Flexible and deep sound design capabilities
  • 💻 Seamless integration as an AUv3 plugin
  • 🎚️ Smooth and responsive controls

Room to improve

  • 🐛 Stability issues, crashes on some devices
  • 🔌 Compatibility problems with newer iOS versions
  • 📂 Preset management could be improved
  • 🔀 Lack of MIDI learn and sequencer features
  • 🖥️ UI scaling issues on larger iPad displays

ButterSynth

From 63 App Store ratings

What we love

  • ✨ Deep sound design capabilities
  • 🎛️ Versatile modulation matrix
  • 🔊 Great sound quality
  • 💡 Innovative wavetable generator
  • 🌟 Serum-like experience

Room to improve

  • 📱 Fiddly on small screens
  • 🐛 Crashes frequently
  • 🐛 Disappears in Cubasis
  • 🐛 Spikes CPU usage
  • 🐛 Crashes on patch change

Bugs and requests

Zeeon synth

Reported bugs

4 issues
  • Preset settings not retained after app restart
  • Synth reverts to default settings when reopening Logic Pro project
  • Crashes and freezes on certain iOS 14+ devices
  • Inability to access in-app purchases from within the app

Requested features

5 requests
  • Add MIDI learn functionality
  • Implement a more robust preset management system
  • Include a built-in sequencer with save/load capabilities
  • Improve UI scaling and layout for larger iPad screens
  • Provide better integration with inter-app audio and Audiobus

ButterSynth

Reported bugs

39 issues
  • App crashing with AUM
  • Disappears in Cubasis randomly
  • Crashes all the time inside Logic
  • Changing a patch spikes CPU to 99%
  • Crashes on every patch change
Show 34 more
  • No audio when rendering or freezing track
  • Keyboard doesn't load on iPhone
  • iOS18 broke ButterSynth (audio recording issues)
  • Failed to load as Auv3
  • Crashes as soon as a preset is selected
  • Some patches hanging/sounding without input
  • CPU spikes to 100% on preset switching
  • Audio crackles on preset switching
  • Sample module has consistent buzz
  • LFOs are extremely simple (no phase offset)
  • Square wave LFO is not square (has slew)
  • Step sequencer always has glide/slew
  • Cannot save custom presets
  • No undo function in wave table editor
  • AUv3 plugin resets when ButterSynth crashes
  • Does not show up as auv3 in Cubasis, AUM, or Audio Evolution
  • Crashes regularly even on newest iPad
  • Preset changes every time play is pressed
  • Not resizing appropriately on smaller screens
  • Crashes with unison function in AUM
  • White noise on crash with unison
  • Sound continues after song stops in GarageBand
  • Preset changes on stop, rewind, or play in GarageBand
  • Keeps crashing in GarageBand (AUv3)
  • Patches in standalone sound different as AUv3
  • Crashes when hitting play with arpeggiator/sequencer on iPhone
  • No keyboard appears in iPhone standalone mode
  • Audio Unit Extension quit error on export
  • Lots of crashes in standalone and hosted in AUM
  • MIDI not working
  • Automation still doesn’t work in Logic Pro
  • Random LFO is great for recording sequences
  • Preset browser closes each time a new preset is selected
  • Works as AUv3 after starting in standalone mode

Requested features

20 requests
  • MPE popup possible on top of the auv3
  • Button to hide built-in keyboard
  • Buffer size option
  • Additional MIDI mappings (e.g., arpeggiator toggle)
  • Sustain pedal support
Show 15 more
  • Longer LFO speed for evolving soundscapes
  • Alternative skins/color themes
  • Pinable preset browser
  • Virtual keyboard to remain active while browser is pinned
  • Make app take up whole screen (no black borders)
  • Master detune
  • Parameter lock
  • More presets
  • Fix square wave LFO to be truly square
  • Fix step sequencer glide/slew for discrete steps
  • Undo function in wave table editor
  • Filter key follow button
  • Adjust envelope curves (especially release)
  • Easier way to adjust modulation matrix amount
  • Phase distortion inclusion

In-app purchases

3 purchases

Zeeon synth

One-time3
  • OI - Exploration Vol. 1$3.99
  • BB Z-Space$4.99
  • BB Synthwave$4.99
None

ButterSynth

No in-app purchases

Questions

Is Zeeon synth free?
Zeeon synth costs $14.99, and also offers in-app purchases.
Is ButterSynth free?
ButterSynth costs $19.99, with no in-app purchases.
Which has better reviews, Zeeon synth or ButterSynth?
Zeeon synth is rated higher. Zeeon synth averages 4.8 out of 5 from 209 ratings, while ButterSynth averages 4.0 from 63 ratings.
Do Zeeon synth or ButterSynth have ads?
Neither Zeeon synth nor ButterSynth shows ads.
Which is updated more often, Zeeon synth or ButterSynth?
Zeeon synth ships an update every 2 months, and ButterSynth every 2 months. Most recently, Zeeon synth was updated on October 20, 2026 and ButterSynth on October 21, 2026.

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