Core Synth HD vs RRS Ivoks
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Core Synth HD
Create music with a powerful monophonic synthesizer for iPad. Explore dual oscillators, customizable filters, and an arpeggiator. Save your custom sounds and enhance your live performances with intuitive controls.
- Dual overlapping oscillators
- Four wave patterns
- Low Pass Filter with ADSR
- Volume Envelope Shaper (ADSR)
- Arpeggiator with multiple modes
- Save unlimited patches
Read full descriptionHide full description
Top free iPad music app in 5 countries, top 10 in more than 50! Get your groove on with Core Synth HD, the definitive monophonic synthesizer for the iPad. With tons of features packed into a small package, Core Synth is great for live performing. A Pitch Wheel replicates perfectly the real thing! This free app has the following features: - Pitch Wheel - 2 Octave keyboard - Keys light up in different colors when pressed Oscillator Module - Dual overlapping oscillators - Four wave patterns: Square, Triangle, Sawtooth and Reverse Sawtooth * Select from 5 octaves * Adjust glide between notes * Fine tune Oscillator 2 with option to sync with Oscillator 1 Volume Envelope Shaper - Edit ADSR (Attack, Decay, Sustain, Release) Low Pass Filter Module - Adjust Cutoff and Resonance - Edit ADSR (Attack, Decay, Sustain, Release) Upgrade to the full version within the app for the following additional features: - 7 Octave Keyboard - Octave control to move along entire range - Modulation Wheel Patches Module - Save an unlimited number of individually named patches - Browse through your collection before applying patch - Delete unwanted patches Modulation Module - Four wave patterns: Square, Triangle, Sawtooth and Reverse Sawtooth - Modulate Filter, Pitch or Wave - Adjust LFO Rate and amount Arpeggiator Module - Arpeggio moves up to 5 octaves - Four step modes: Up, Down, Up/Down, Random - Adjust rate Many more exciting enhancements to follow! Core Synth HD includes open source code from MobileSynth developed by Allen Porter.
RRS Ivoks
This app emulates analog synthesizers, offering a range of sound shaping tools including oscillators, filters, and amplifiers. It supports AUv3 hosting for integration with music production apps and provides extensive MIDI control.
- Analog Emulation
- AUv3 Compatible
- Dual Oscillators
- Filter Block with ADSR
- Amplifier Block with ADSR
- Modulation (LFO) Controls
- MIDI CC Implementation
Read full descriptionHide full description
RRS Ivoks AUv3 instrument — comes as time-limited Demo-version for you to try. It gives you 5 minutes of Free play time. (You can reload the RRS Ivoks AUv3 instrument as many times as you want, thereby you get the Demo period again and again.) Unlimited version of RRS Ivoks AUv3 instrument comes as In-App Purchase. Features: • Analog Emulation; • Undo/Redo; • A/B comparison; • 2x/4x/8x Upsampling; • Macro controllers; • Scalable GUI. On the centre panel are located two audio-frequency oscillators: • OSC1 offers frequency Band regulator, five Waveforms and controls for LFO Modulation level plus OSC2 Cross-modulation; • OSC2 offers the same frequency Band and Waveforms, an independent control for Modulation depth, plus Detuning. Underneath these located the mixer, which offers level controls for the two Oscillators, the Noise generator, and Saturation Drive. To the right of these, located the filter block. The top half is a standard ADSR envelope — until you flip the switch «Envelope mode», when it becomes a repeating AD-envelope instead. The four controls at the bottom adjust Cut-off, Resonance, LPF to BPF switch, Modulation level and Envelope level. Next after the filter is the amplifier block, it also has ADSR envelope along with another Modulation level and Velocity sensitivity control. Again, the envelope can be switched to a Repeating Mode that generates a triangular waveform determined by the Attack and Decay settings, providing some of the instrument’s most distinctive effects. The leftmost panels house the Modulation (LFO) controls (top), Mode which offers four waveforms, including noise, and a stepped Function for sample & hold (S&H) effects, well as Speed control. And global settings such as the master Tune, master Volume, Legato mode, Monophonic and Duophonic operation and Unison switches, and the Glide control. To use Ivoks as an instrument, you need an AUv3-compatible host app like GarageBand, Auria, AUM, Cubasis and more — RRS Ivoks will appear in the list of Audio Unit instruments in the host app. MIDI CC Implementation Chart: • CC#003 => HQ • CC#009 => Saturation Drive • CC#014 => Modulator Speed • CC#015 => Modulator Mode • CC#020 => Filter Attack • CC#021 => AMP Attack • CC#022 => Filter Decay • CC#023 => AMP Decay • CC#024 => Filter Sustain • CC#025 => AMP Sustain • CC#026 => Filter Release • CC#027 => AMP Release • CC#028 => Filter Envelope Mode • CC#029 => AMP Envelope Mode • CC#030 => OSC1 Band • CC#031 => OSC2 Band • CC#085 => OSC1 Waveform • CC#086 => OSC2 Waveform • CC#087 => OSC1 XMod • CC#089 => OSC2 Detune • CC#090 => MOD to OSC1 • CC#102 => MOD to OSC2 • CC#103 => OSC1 Level • CC#104 => OSC2 Level • CC#105 => Noise Generator • CC#106 => Global Tune • CC#107 => Global Glide • CC#108 => Global Volume • CC#109 => Global Voice • CC#110 => Global Unison • CC#111 => Global Retrig • CC#112 => Filter Cut-off • CC#113 => Filter Resonance • CC#114 => Filter Mode • CC#115 => MOD to Filter • CC#116 => Filter Envelope • CC#117 => MOD to AMP • CC#118 => Velocity Sensitvity
Screenshots
Verdict
The clearest difference is rating: RRS Ivoks at 4.4 against Core Synth HD's 3.4. RRS Ivoks also leads on review sentiment (63% vs 31%) and update cadence (fortnightly vs every 4 months). Core Synth HD's advantage is iOS requirement (8.0 vs 10.0). On price, ads, in-app purchases and monetization model 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
Both are free to download. Core Synth HD sells 1 one-off in-app purchase and RRS Ivoks sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.
RRS Ivoks holds the better App Store score, 4.4 against 3.4. That said, the two scores are not equally well evidenced: RRS Ivoks has 46 ratings behind it against 5, so its average is the more settled of the two. Written reviews point the same way: 31% of Core Synth HD's written reviews are positive against 63% of RRS Ivoks's.
Core Synth HD ships an update every 4 months, RRS Ivoks fortnightly. The most recent releases landed on October 20, 2026 and October 24, 2026 respectively.
| Parameter | Core Synth HD | RRS Ivoks |
|---|---|---|
| Price | Free | Free |
| Rating | 3.4 (5 ratings) | 4.4 (46 ratings) — better |
| Positive reviews | 30.6% of reviews | 63.3% of reviews — better |
| Number of ratings | 5 | 46 — better |
| Update frequency | Every 4 months | Fortnightly — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free with in-app purchases | Free with in-app purchases |
| Devices | iPad | iPhone, iPad, iPod — better |
| Requires iOS | 8.0 — better | 10.0 |
| Further details — not scored | ||
| Size | 10 MB | 19 MB |
| Age rating | 4+ | 4+ |
| Developer | Core Engine Apps | RRS, OOO |
Customer experience
Core Synth HD
RRS Ivoks
Bugs and requests
Core Synth HD
Reported bugs
21 issues- No sound on iPad Pro
- No sound on iOS 12
- No sound since last update
- Program doesn't start after update
- Ad blocks view
Show 16 moreShow fewer
- App crashes on load
- App crashed frequently
- Rarely produced sound
- Annoying clicking noise when playing a note
- Stopped playing notes after a while
- App reset to free module after purchase
- Lost saved presets after update
- CS doesn't work after iOS6 update
- Sound quit working suddenly
- No sound after purchase
- No audio on iPad 2
- Keyboard stops making noise after playing
- Crashes on every load
- Clipping pops and clicks
- Audible clicks between notes
- Constant click with the sounds
Requested features
17 requests- Add MIDI support
- Add Audiobus support
- Add recording with copy/paste
- Add sine wave for sub basses
- Add polyphony option
Show 12 moreShow fewer
- Add tempo sync delay, flange, chorus
- Add bit reduction
- Fix modulation clipping
- Fix clicking/popping sounds
- Add manual
- Add more presets
- Add noise generator
- Add detuning on both oscillators
- Add ability to map LFO to mod wheel
- Add switch to turn arpeggiator on/off
- Add Core Midi and MIDI over wifi support
- Fix Osc Octave Text numbering
RRS Ivoks
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Core Synth HD
- Full Version Upgrade$1.99
RRS Ivoks
- RRS Ivoks Unlimited$8.99









