# iSEM Synthesizer vs OB

The clearest difference is price: iSEM Synthesizer at $9.99 against OB's $14.99. iSEM Synthesizer also leads on review sentiment (74% vs 57%) and iOS requirement (12.1 vs 15.0). OB's advantage is rating (4.3 vs 4.1) and update cadence (every 2 months vs every 5 months). On ratings volume, ads and in-app purchases there is nothing between them.

iSEM Synthesizer costs $9.99 and OB $14.99 up front. Neither carries in-app purchases, so what you see is what you pay.

OB holds the better App Store score, 4.3 against 4.1. Both are backed by a comparable volume of ratings — 60 and 64 respectively. Written reviews complicate that: 74% of iSEM Synthesizer's written reviews are positive against 57% of OB's, so the app with the better star average is not the one people write more warmly about.

iSEM Synthesizer ships an update every 5 months, OB every 2 months. The most recent releases landed on October 23, 2026 and October 29, 2026 respectively.

## The numbers

| Metric | iSEM Synthesizer | OB |
| --- | --- | --- |
| Price | **$9.99** | $14.99 |
| Rating | [4.1 (60 ratings)](https://appshunter.io/ios/app/isem-synthesizer/id673921187/reviews) | **[4.3 (64 ratings)](https://appshunter.io/ios/app/ob-xd-auv3-synth/id1465262829/reviews)** |
| Number of ratings | 60 | **64** |
| Positive reviews | **73.7% of reviews** | 57.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 5 months | **Every 2 months** |
| Monetization | Paid | **Free** |
| Best chart rank | — | **#199** |
| Size | 80 MB | 25 MB |
| Requires iOS | **12.1** | 15.0 |
| Devices | iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Arturia](https://appshunter.io/developer/549089551) | [DiscoDSP LLC](https://appshunter.io/developer/1465262828) |

## What reviewers say

### iSEM Synthesizer

[App page](https://appshunter.io/ios/app/isem-synthesizer/id673921187)

This app is a touch-based emulation of the classic 1974 Oberheim SEM synthesizer, known for its warm analog sounds. It offers a wide range of sonic possibilities, from fat basses to lively leads, and includes over 500 preset sounds.

**Highlights:** Classic Oberheim SEM emulation, Two oscillators with PWM, 12dB/oct multi-mode filter, Added LFO, Noise, Sub oscillator, Arpeggiator, Portamento, Polyphonic playability, 500+ preset sounds, MIDI and AudioUnit v3 support

**Features:** macOS Compatibility

**In-app purchases:** none

**What reviewers like**

- 🎹 Fantastic sound quality
- 💯 Faithful to the original Oberheim SEM
- 🎨 Versatile sound design capabilities
- 🎚️ Intuitive and responsive interface
- 🔊 Rich, warm, and analog-like tones

**What reviewers complain about**

- 🐛 Frequent crashes and stability issues
- 🔌 Poor integration with DAWs and MIDI controllers
- 🕰️ Slow preset loading times
- 🔇 Limited modulation options compared to hardware
- 🤔 Uninspiring factory presets

**Reported bugs**

- Preset loading issues
- MIDI connectivity problems
- Unexpected crashes when switching between presets
- Envelopes causing clicks and pops in some patches
- Unresponsive controls when used as an AUv3

**Requested features**

- Add MIDI program change support
- Improve preset management and organization
- Implement a global tuning option
- Enhance MIDI mapping and automation capabilities
- Provide more comprehensive AUv3 support


### OB

[App page](https://appshunter.io/ios/app/ob-xd-auv3-synth/id1465262829)

**Currently charting:** #199 Top Paid · Music (US App Store)

This app emulates the classic Oberheim OB-X synthesizer, offering its rich sound and behavior with added enhancements. It focuses on sonic quality and includes micro random detuning for authentic analog warmth. External effects are recommended to further shape its versatile soundscapes.

**Highlights:** Oberheim OB-X emulation, Recreates original sound and behavior, Added enhancements to original design, Micro random detuning, Rich and good sound quality

**Features:** macOS Compatibility

**In-app purchases:** none

**What reviewers like**

- 🎶 Incredible sound quality
- ✨ Inspiring creative tool
- 🎹 Faithful emulation of classic synth
- 🎛️ Great for programming
- 🎚️ Useful presets

**What reviewers complain about**

- 🐛 Unusable UI on older devices
- 💻 Poor GUI scaling on iPad Pro
- 🎛️ Controls unresponsive or misaligned
- 📉 Limited functionality without updates
- 🤷‍♂️ No clear upgrade path

**Reported bugs**

- Crashes in Audiobus
- Cannot use in MIDI section of Audiobus
- Preset browser issues (scrolling, cut off banks)
- Automation bug with cutoff freq
- UI issues on iPad Pro (buttons misaligned, text cut off)

**Requested features**

- Add last/high priority for mono patches
- Increase polyphony to 8 voices
- MIDI Learn functionality
- Preset browser improvements (categories, scrolling)
- Adjustable keyboard size


## Frequently asked questions

### Is iSEM Synthesizer free?

iSEM Synthesizer costs $9.99, with no in-app purchases.

### Is OB free?

OB costs $14.99, with no in-app purchases.

### Which has better reviews, iSEM Synthesizer or OB?

OB is rated higher. iSEM Synthesizer averages 4.1 out of 5 from 60 ratings, while OB averages 4.3 from 64 ratings.

### Do iSEM Synthesizer or OB have ads?

Neither iSEM Synthesizer nor OB shows ads.

### Which is updated more often, iSEM Synthesizer or OB?

iSEM Synthesizer ships an update every 5 months, and OB every 2 months. Most recently, iSEM Synthesizer was updated on October 23, 2026 and OB on October 29, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*