# FM 304 — FM Groovebox

> Three 4-operator FM synths with sequencers and effects for music creation. (iPhone/iPad app by Paul Betowski.)

- Source: https://appshunter.io/ios/app/fm-304/id1449167984 (this page in markdown: same URL + `.md`)
- Developer: [Paul Betowski](https://appshunter.io/developer/538476580)
- Category: Music
- Price: $3.99
- Rating: 4.75/5 from 4 App Store ratings · 3 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.0 · 17 MB
- Languages: English
- Released: 2019-04-14
- Data updated: 2026-07-07
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/fm-304/id1449167984/reviews.md

## What is FM 304?

FM 304 — 3x FM Synth Groovebox

FM 304 is a powerful trio of 4-operator FM synthesizers, each with its own sequencer and effects. Built for fast, hands-on sound design, every parameter is available with a one-knob-per-function layout — no menus, no digging.

Create evolving patterns, punchy sequences, and complex FM textures in seconds. Everything is on screen, ready to tweak, making it easy to move from idea to finished loop without breaking flow.

Features

• 3 independent 4-operator FM synthesizers
• Immediate one-knob-per-function control
• 3x 16-step sequencers (one per synth)
• Built-in effects: delay, reverb, chorus
• 3x LFOs for modulation
• 8 FM algorithms
• Note frequency quantisation
• 100 save slots

Designed for speed

No menu diving. No setup.
Just pure FM synthesis with everything visible and playable.

## Key features

- Three 4-operator FM synths
- Integrated sequencers
- Onboard delay, reverb, and chorus effects
- One knob per function control
- 100 save slots
- 8 algorithms
- Note frequency quantize

## Recent user reviews (3 of 3)

All indexed reviews: https://appshunter.io/ios/app/fm-304/id1449167984/reviews.md

### 5/5 — ❤️ it

*2020-12-09*

Can have some fun little sessions with this one. Thanks for the update! Wish it had some multiout action and a tap tempo button and a pretty please for auv3 on all your groove box apps ;0
Also I love the app design on your apps very well done quite beautiful thanks!

### 5/5 — fm sequencing madness!

*2019-04-22*

sounds great and alot of fun!i wish the knobs were bigger its hard to adjust on ipad mini .

### 5/5 — Mind blowing fm beats

*2019-04-13*

Very unique, and 4 fm drum synths in a window with all parameters! I feel the need to be minimal as is the app, yet the results are very intense and insane fm capacity overflowing the wires in the mind of the iPads soul. Seriously great idea to just put all the knobs and sliders on one page to ease the overwhelm.

## Frequently asked questions about FM 304

### What is FM 304?

FM 304 is a music creation application for iPad that features three 4-operator FM synthesizers, each equipped with integrated sequencers and onboard effects like delay, reverb, and chorus.

### How much does FM 304 cost?

FM 304 is a paid application, priced at $3.99. This one-time purchase grants you full access to all its features.

### What devices does FM 304 support?

FM 304 is designed exclusively for iPad devices, offering a tailored experience for Apple's tablet platform.

### How often is FM 304 updated?

The application was last updated on December 8, 2020, with version 1.1.0. While updates may not be frequent, the app is stable and functional.

### What is the age rating for FM 304?

FM 304 has an age rating of 4+, making it suitable for a wide range of users interested in music creation.

### Can I save my creations in FM 304?

Yes, FM 304 provides 100 save slots, allowing you to store and recall your unique sounds and tunes.

### What kind of effects are included in FM 304?

FM 304 includes essential onboard effects to enhance your sound design, such as delay, reverb, and chorus.

### Does FM 304 have ads?

As a paid application, FM 304 does not contain advertisements. You can enjoy an uninterrupted music creation experience.

## Version history (last 3 releases)

### 1.1.5 — 2026-04-28

Bug fixes

### 1.1.0 — 2020-12-08

Audiobus 3 support
Inter-App Audio support
Background audio
Knob sensitivity adjusted for some parameters
Tempo calculation error fixed
Screen size scaling improvements

### 1.0 — 2019-04-13

No release notes.

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## More apps by Paul Betowski

- [DUBSTEP / Loops / Keyboard / Drums](https://appshunter.io/ios/app/dubstep-loops-keyboard-drums/id557267838)
- [E Theremin – Electro Theremin](https://appshunter.io/ios/app/e-theremin-electro-theremin/id591471950)
- [SynthDrum Pads](https://appshunter.io/ios/app/synthdrum-pads/id657577819)
- [DNB / Loops / Synth](https://appshunter.io/ios/app/dnb-loops-synth/id670737604)
- [E–Theremin MKII](https://appshunter.io/ios/app/etheremin-mkii/id905407070)
- [WubSynth](https://appshunter.io/ios/app/wubsynth/id1074423582)

All apps by Paul Betowski: https://appshunter.io/developer/538476580

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-07-07.*