Comparison

iSEM Synthesizer vs OB

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

Head to head
About

iSEM Synthesizer

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
Read full description

COMPATIBILITY Apple’s AudioUnit v3, Inter-App Audio connectivity, AudioBus 3, Korg’s WIST and Apple’s CoreMIDI are all supported. Furthermore, iSEM is fully compatible with the Audio Unit Extension format. It can be directly launched in any Audio Unit host applications. DESCRIPTION iSEM is a recreation of the classic 1974 Oberheim SEM (Synthesizer Expander Module), one of the world's first self-contained synthesizer modules and the first to bear the "Oberheim Electronics" name. The Oberheim SEM was made famous by artists and bands such as Lyle Mays, Jan Hammer, Joseph Zawinul, Supertramp, 808 State, Vince Clarke and Depeche Mode. Based on the TAE® technology found in our Oberheim SEM V software, iSEM brings back the sound and special characteristics of this iconic synth in an sonically accurate and expanded touch-based emulation. What you can do with the iSEM? The iSEM is a powerful instrument capable of producing a wide range of warm analog sounds.  Reproducing the unique SEM architecture, with its oscillator sync, characteristic filter shape and specific envelope response, the iSEM is able to generate the fat basses that have made the Oberheim brand so popular. Thanks to its simple and clever PW and pitch modulations, it is also very easy to produce moving and lively leads. Its remarkable 12 dB/oct multimode filter is a real blast from the past, becoming an awesome weapon in the context of current electronic music. This unique module can instantly tailor your sound to fat, crisp, or spectral textures with access to all the nuances in between… iSEM comes with over 500 sounds that you can browse through and play. You can also easily create your own sounds with the easy to use interface. Play iSEM's numerous sounds from the iPad keyboard or control iSEM from a MIDI keyboard or other app via CoreMIDI and integrate it into your studio or live performance. If you are an owner of of the Arturia SEM V software on your Mac or PC, you can even import and export sounds between your laptop or desktop SEM V and iSEM. FEATURES All the original parameters of the Oberheim SEM: two oscillators, each offering sawtooth wave and variable-width pulse wave with PWM, sine wave LFO, 12dB/oct multi-mode Filter with low-pass, high-pass, band-pass and notch, two ADS envelope generators. Added functionalities: New LFO, Noise, Sub oscillator, Arpeggiator, Portamento. Polyphonic playability 8 Voice Programmer module allows each voice to have different settings HOLD and CHORD modes. Virtual Analog Chorus. Virtual Analog Delay. Full user MIDI mapping of panel controls. Supports WIST sync to other iOS devices. Support of AudioUnit Extension, AudioBus 3 and Apple’s Inter-App Audio connectivity. The Oberheim™ name used here is a trademark of the Gibson Guitar Corp. The trademark is used by license to Arturia.

About

OB

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
Currently charting
Read full description

OB-Xd is based on the Oberheim OB-X. It attempts to recreate its sound and behavior, but as the original was very limited in some important ways, a number of things were added or altered to the original design. OB-Xd was designed to sound as good and as rich as the original. It implements micro random detuning. Also, like many synths of the OB-X's generation, the OB-Xd has no internal effects so its sounds and textures can be greatly enhanced by the use of additional processing like chorus, reverb, delay, etc.

Screenshots

OB1 screens

Verdict

The call

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.

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

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

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard8 real differences · 3 level
iSEM Synthesizer versus OB: the parameters behind the verdict, then further details
ParameteriSEM SynthesizerOB
Price$9.99 — better$14.99
Rating4.1 (60 ratings)4.3 (64 ratings) — better
Positive reviews73.7% of reviews — better57.0% of reviews
Number of ratings6064 — better
Update frequencyEvery 5 monthsEvery 2 months — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
Best chart rank—#199 — better
DevicesiPadiPhone, iPad, iPod — better
Requires iOS12.1 — better15.0
Further details — not scored
Size80 MB25 MB
Age rating4+4+
DeveloperArturiaDiscoDSP LLC

Customer experience

iSEM Synthesizer

All ratings60 ratings
Positive75.0%
Neutral8.3%
Negative16.7%
Written reviews243 reviews
Positive73.7%
Neutral9.1%
Negative17.3%

OB

All ratings65 ratings
Positive84.6%
Neutral4.6%
Negative10.8%
Written reviews86 reviews
Positive57.0%
Neutral12.8%
Negative30.2%

User reviews

iSEM Synthesizer

From 60 App Store ratings

What we love

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

Room to improve

  • 🐛 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

OB

From 64 App Store ratings

What we love

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

Room to improve

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

Bugs and requests

iSEM Synthesizer

Reported bugs

5 issues
  • 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

5 requests
  • 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

Reported bugs

13 issues
  • 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)
Show 8 more
  • App suspends on iOS 14
  • No virtual keyboard in standalone app
  • AUv3 crashes when adding second instance
  • UI messed up in AU
  • Knobs don't line up with display
  • Wonky controls
  • Programmer page without menu, cannot save/open patches
  • LFOing filter cutoff jerky

Requested features

19 requests
  • Add last/high priority for mono patches
  • Increase polyphony to 8 voices
  • MIDI Learn functionality
  • Preset browser improvements (categories, scrolling)
  • Adjustable keyboard size
Show 14 more
  • GUI scaling/layout redesign for iPhone
  • Skins for GUI
  • MIDI keyboard in standalone mode
  • Effects
  • Preset manager
  • Zoom functionality for AUv3 on iPhone
  • Fix knob turning bugs
  • Add patch select in DAW apps
  • GUI color scheme options
  • Manual in settings
  • Import presets
  • Layering sounds (like original OBXa)
  • White pinstripes on blue background (cosmetic)
  • Mod wheel customization

In-app purchases

None

iSEM Synthesizer

No in-app purchases

None

OB

No in-app purchases

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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