AUFX vs ButterSynth
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
AUFX
This app offers a versatile stereo dynamics processor with advanced features like a noise gate, compressor/expander, and limiter. It allows for a wide range of audio manipulation, from subtle adjustments to extreme effects, with external side-chain capabilities and high-quality DSP.
- Stereo dynamics processor
- Noise gate
- Compressor/expander
- External side-chain input
- Lookahead limiter
- High quality 32-bit DSP
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A highly tweakable stereo dynamics processor with noise gate, compressor/expander with external side-chain input, and limiter/clipper. From subtle compression, extreme pumping, to maximum loudness! This app is part of the AUFX series, a collection of simple and powerful audio effect apps. • High quality 32-bit DSP engine. • Compressor/expander with optional lookahead buffer. • Allows negative ratios for pumping/cancellation effects. • Hard or soft knee with adjustable radius. • Built-in side-chain low/high cut filters with monitor toggle. • External side-chain input through Inter-App Audio or Audiobus. • Built-in noise gate. • Brick-wall lookahead limiter. • Hard/soft clipper. • Supports "parallell compression". • RMS/Peak envelope followers with attack, release and hold time. • Switchable between Linear and Logarithmic mode. • Automatic makeup gain. • Stereo link on/off. • Process hardware input/output, or other apps through Inter-App Audio or Audiobus (input/filter/output slots supported). • Save, load and share user presets. • Supports Audiobus 2 state saving. • Comes with several bundled presets. • Fully MIDI controllable, including Virtual MIDI. • Background Audio. • Record the result directly in app. • Email recordings or export to AudioShare audio document manager app. • Access user presets and recordings through iTunes File Sharing.
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.
- 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
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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
Verdict
The clearest difference is price: AUFX at $4.99 against ButterSynth's $19.99. AUFX also leads on rating (4.3 vs 4.0) and iOS requirement (9.0 vs 14.0). On review sentiment, ratings volume, update cadence and ads 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
AUFX costs $4.99 and ButterSynth $19.99 up front. Neither carries in-app purchases, so what you see is what you pay.
AUFX holds the better App Store score, 4.3 against 4.0. Both are backed by a comparable volume of ratings — 32 and 63 respectively. Written reviews point the same way: 66% of AUFX's written reviews are positive against 59% of ButterSynth's.
AUFX ships an update every 5 months, ButterSynth every 2 months. The most recent releases landed on October 9, 2026 and October 16, 2026 respectively.
| Parameter | AUFX | ButterSynth |
|---|---|---|
| Price | $4.99 — better | $19.99 |
| Rating | 4.3 (32 ratings) — better | 4.0 (63 ratings) |
| Positive reviews | 65.8% of reviews — better | 59.2% of reviews |
| Number of ratings | 32 | 63 — better |
| Update frequency | Every 5 months | Every 2 months — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 9.0 — better | 14.0 |
| Further details — not scored | ||
| Size | 5 MB | 468 MB |
| Age rating | 4+ | 4+ |
| Developer | Kymatica AB | Arto Vaarala |
Customer experience
AUFX
ButterSynth
Bugs and requests
AUFX
Not enough reviews yet to summarise bugs or requests.
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
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- 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 moreShow fewer
- 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
AUFX
No in-app purchases
ButterSynth
No in-app purchases









