What Sonos won't let you do, a Belgian engineer sells you for $2.99: Sonority and the business of filling gaps that "officially aren't open"

On the last day of 2025, Casper Verswijvelt, a software engineer in Ghent, Belgium, posted on Reddit's r/sonos: "I'm building an app that lets every Sonos setup add front speakers." Half a year later, the app, called Sonority, hit the App Store and reached #1 on Hungary's Music paid chart and #2 in Denmark, charting in 19 countries in total. It sounds like a small hit. But by Nov 6, it had only 2 ratings in the US and hadn't grown in 10 days. This piece covers what got it its first users, why it's struggling to scale, and whether you can build a business on "unlocking features closed hardware officially doesn't offer."

What it is

Sonos is a US home audio brand. Its speakers "bind" to each other over home Wi-Fi: a soundbar plus two rear surrounds and a subwoofer make a home theater. The official app only allows a few fixed combinations. But Sonos speakers expose some undocumented interfaces on the local network, which can do more binding than the official app lets you.

Sonority puts those interfaces to use. The first line of its App Store page reads: "Sonority configures your speakers in ways the official control app doesn't allow… it creates standard, supported bindings, but the official app chooses not to offer them." What it can do:

• Add a separate pair of front left and right speakers to a soundbar, so the soundbar only handles center. The community has wanted this feature since 2013;
• Pair speakers of different models into a stereo pair (the official app blocks this), with 2 to 16 speakers forming one zone;
• 10-band EQ, where the official app only has bass and treble;
• Save a full layout as a snapshot, restore it with one tap after moving speakers, and apply it directly from a home-screen widget.

It sells on iOS for a one-time $2.99, with no subscription. The author is a senior software engineer at a smart-home company in Belgium and previously built open-source Android apps. The app is written in Flutter, one codebase for iOS, Android, and macOS, and was built with AI-assisted coding. Version numbers only reached 2 by Nov 0.9.1, with frequent updates.

Discovering this need isn't what made it work.

Before Sonority, German developer Marcus Pleintinger's SonoSequencr had been selling for ten years. It started as a scene-sequencing tool. Then he added an experimental feature: putting front speakers in front of a Sonos soundbar. 2025 March, a YouTube channel, NeverEnoughTech, posted a video about the feature that hit 54k views. 2026 January, someone on r/sonos wrote that they had "caught the SonoSequencr wave." Feb 6 to 8, a batch of five-star US reviews for SonoSequencr all said "added front speakers." It has 116 ratings in the US and its own subreddit.

So when Sonority showed up, "Sonos can take front speakers and it sounds much better" was already well explained. It was the second entrant.

How it got its first users

Building and asking on Reddit at the same time. Under 2025-12-31's post, the comments said two things that more or less set the product direction: "Unless you build for Android, I can't see how it's better than SonoSequencr"; and "SonoSequencr's biggest problem is that adding front speakers drops Trueplay (Sonos's automatic tuning)." SonoSequencr was iOS-only, so Android users had to borrow an iPhone to set it up. Sonority shipped an Android version first.

Easy to use. A guided home-theater setup flow, a progress bar at every step, an automatic restore point before any change, and one-tap undo. Aug 9, someone on r/sonos posted "SonoSequencr or Sonority? Has anyone tried both?" A reply said, "sonority is easier to use… my main phone is Android." Sep 30, under a post complaining about the Beam Ultra, someone recommended "there's a newer app called Sonority, much easier to use."

The developer jumped in personally. Oct 5, in a thread titled "Is the Beam Ultra worth it?", the author replied "Sonority dev here" and asked users to export a diagnostic bundle from the app and send it to him. The app has a dedicated diagnostics feature built for one-on-one troubleshooting in the community.

A foreign-language press piece. Czech outlet AVmania published a long hands-on article in Jul 17, titled "Where the manufacturer hesitated, the community filled the gap," using an Arc Ultra with two One speakers as the front channels. At the time the iOS app sold for about 1 euros, and the article said that price only covered the developer account fee. Hungary and Slovakia were where it climbed highest on the paid charts, possibly because of this article (inference).

People brought in by new hardware. Sonos released the new soundbar Beam Ultra this fall. 9, October, r/sonos was full of new-buyer posts, and some of them turned to look for "how to add front speakers" and found this app through recommendations (inference).

Not found: paid ads, TikTok, discussion on X, dedicated YouTube reviews, Product Hunt. All users came from this one r/sonos circle, plus people searching "for Sonos" in the store.

How the chart positions came about

The Music category Top Paid bar is very low: in a small country, a few sales a day can put you in the top 10, and in the US, reaching the top 100 probably takes somewhere between a few and a dozen sales a day (inference). Ratings have been flat for 10 days, which suggests the chart position is held up by sporadic purchases, not a surge of users. Revenue is estimated at a few dozen to a few hundred dollars a month (rough estimate).

It has been quietly moving toward charging

Two things are worth noticing. First, its original GitHub repo has been unreachable since Nov 6 (made private or deleted). Second, the Android version: in August the Google Play listing was a free version with 500+ downloads. As of Nov 6 that page is 404, and the official site sonorityapp.com now links to a different, newly listed "Sonority" priced at $2.79 one-time, with 50+ downloads and an update in Oct 27.

Free on Android to build reputation, paid on iOS to recoup costs was the approach that set it apart from SonoSequencr. Now both platforms charge and the code is no longer public, which suggests the author is moving toward making real money (inference). But the Android first-mover advantage has to be rebuilt from 50 downloads.

Who it's competing with

• SonoSequencr: the old rival, iOS only. Users call it "a bit janky," and adding front speakers drops Trueplay. Same price, $2.99, with a subscription option too.
• Somos InControl: a new rival, still in iOS TestFlight and Android closed testing. It's a full-featured Sonos remote (volume, presets, lock-screen live activity), and it also supports independent front speakers and stereo pairs. The basic features are free, and multi-room features are a one-time purchase. Once it launches publicly, Sonority's "configuration only" pitch will look thin.
• Sonos official: in Nov 3, the 91.0 release just added Presets (one-tap restore of room, source, and volume), but it still lacks EQ and grouping (TechTimes, 11-04). The community has been asking for front-channel support for 13 years. If the official app opens it up someday, or firmware blocks these interfaces, the core value of apps like this disappears.

If it were you

In one line: you don't need to chase Sonority itself. The Sonos front-channel pool is small and already split among three players. What's worth learning is its playbook: find features in closed hardware where the interface is technically reachable, the manufacturer doesn't open it, and users have wanted it for years, then package it as a few-dollar one-time-purchase tool. It's a craft that can earn pocket money, not a business that scales.

• Who it suits: developers who understand LAN protocols and are willing to capture traffic and read private interfaces; people who are heavy users of a hardware ecosystem and already well known in its community.
• Who it doesn't suit: people who want steady monthly income, or who aren't willing to accept the risk that a single manufacturer firmware update can break everything.
• How to do it: find the scenario before you write code. Three standard checks: there's a feature that people have requested for years on the manufacturer's official forum with no response; the local interfaces (UPnP, SOAP, BLE, LAN HTTP) can actually do it; existing third-party tools cover only one platform or are hard enough to use that people complain. You could look at ecosystems like smart lights, robot vacuums, NAS, cameras, and car infotainment (inference). Copy Sonority's features: guided setup, automatic backup before changes, one-tap undo, configuration snapshots. Flutter plus AI coding lets one person ship to three platforms at once.
• How to get users: build in public in the brand's subreddit and Facebook user groups, and make your first post ask "what do you want most?" to rank needs by comments. After launch, answer questions in the thread yourself, and include a button that exports diagnostic info. Put "for [brand name]" in your store name to catch search traffic. Get one or two small-language audio/video outlets to publish hands-on reviews.
• When to move: the few months after a manufacturer launches new hardware are the most valuable (new buyers look for ways to use it), and also when the manufacturer is most likely to tweak firmware. Get in before the official app adds the feature itself.
• Signs you've misread it: After a month of posting in communities, no one has written a comparison or recommendation post on their own; or after launch the rating count stays in single digits. The first means demand is too small. The second means you're in the same spot as Sonority, reaching only a small group of people.

A reminder for anyone using charts to find opportunities: in category Top Paid charts like Music, a few sales in a small country can land you in the top three. Check whether ratings are growing before you check the rank.