King of FM is a free, professional-grade FM synthesizer app for iOS and Mac that provides authentic 80s hardware sounds.
The App DNA
What makes this app unique?
Users hire King of FM for high-fidelity, retro-synth sounds without the cost of hardware or subscription-gated software, serving the need for accessible professional production tools.
For Music producers, songwriters, and keyboardists looking for authentic 80s FM synthesizer sounds for mobile and desktop production.
What does it look like?
Key features
Provides 300+ presets and 10,000+ samples derived from DX7 and SY77 hardware.
Functions as a plugin within iOS hosts like GarageBand, AUM, and Cubasis for integration into mobile production workflows.
Allows import of Scala .scl tuning files and selection of 60+ international scales.
How much does it cost?
The app operates as a free, volunteer-led project with no ads or subscriptions, functioning as a brand-building tool for the AudioKit open-source framework.
Velocity
Maintenance developmentnew contentinternationalizationShow more...
The app currently operates at a maintenance cadence, with only one release identified in the recent window. The latest version represents a major feature expansion, focusing on musical customization through microtonal scales and international tuning support. Development appears to be feature-driven rather than high-frequency, with no evidence of recurring live operations or rapid iterative cycles. Future momentum remains to be seen based on whether this update signals a return to active development.
Who built it?
AudioKit Pro
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Retro Keys: Piano, Wurl, RhdsUser Sentiment
What do users think recently?
How are ratings & reviews evolving?
Not enough recent reviews to extract reliable themes yet.
Read the full review analysisCompetition
Competitive landscape for King of FM: DX Synth/E Piano
How's the Music market?
King of FM maintains a strong position in the music category with a 4.88-star rating across 1,741 reviews. Its free, professional-grade offering creates a high barrier for paid competitors in the mobile synth space.
Read the market outlookThe rivals identified
Unlock the deeper market read.
Access the full report for freeThe Analyst's Read
Key takeaways for King of FM: DX Synth/E Piano
Where is it heading?
The mobile music production market is consolidating around high-fidelity, plugin-compatible instruments. King of FM remains advantaged by its zero-cost, high-quality offering, but its reliance on volunteer labor limits its ability to respond to commercial rivals, so the team must focus on high-impact feature updates to maintain its lead.
- The latest release added microtonality and world scales, signaling active feature investment rather than maintenance mode.
- The volunteer-led development model remains the primary constraint on the app's ability to scale features against commercial rivals.
The SWOT
- High-fidelity sample library functions as a B2B distribution barrier into professional studio workflows
- AUv3 plugin architecture enables deep integration into existing mobile production hosts
- Education partnerships could leverage the app's microtonal support for music theory instruction
Next best moves
Audit user-requested features because the current volunteer-led cadence risks stagnation → maintain competitive parity
The counter-intuitive read
The app's status as a free, volunteer project is its primary defensive barrier…
Read the full takeSince the last report: The app's competitive positioning shifted from a focus on financial sustainability to a defensive strategy that leverages its free, high-fidelity status to challenge paid market rivals.
Bottom line
King of FM defends its category lead through authentic sound quality and free access, but the volunteer-led maintenance model risks stagnation against rivals with faster update cycles, so the team should prioritize a clear roadmap to sustain user interest.
Unlock 2 critical frictions, 1 market threat and the analyst’s take.
Access the full report for freeSources
- [1] App Store, source
Report last updated