Hifee: my own music player for the Mac

Hifee is the music player I use all day at my desk. It plays my local lossless library bit-perfect to my audio interface, sends it to my Sonos speakers around the house, adds Apple Music for discovery, and does nothing else. It replaces Audirvana, which I used since 2021.

I didn't write the code. I described what I wanted and my AI agent built it, tested it and shipped it. The why is in The era of personal software is here. This note covers what Hifee does and how it works.

Why I built it

I had 2 apps and wanted neither of them:

• Audirvana plays local files well, but it's heavy, its playlists are clunky, and I pay a subscription for features I don't use.
• Apple Music is good for finding new music, but it doesn't do bit-perfect playback with sample-rate switching for a local library of FLAC files.

I wanted 1 app with only my features, in my own design, controlled from my keyboard and from Alfred. The name follows the -ee family of my tools, next to Dictee: my own local dictation app and Stickee: sticky notes that go full screen on every monitor.

What it does

The Prompter layout uses tabs instead of a sidebar, so it stays readable at 1024x600:

Playlists use a real table, with a column for each field and a click on a header to sort:

And ⌘K opens the Command Centre, so I never have to remember a shortcut:

Memory

I measured the 3 apps on the same day, with the same library of about 29,000 tracks:

Apple Music had almost no local library at the time, and it still used 2x more than Hifee. Memory matters more to me than it used to, because my local AI models need it.

For business people

Hifee is a personal tool for 1 user. It shows what a non-developer can now get from an AI agent: a native app that replaces a paid subscription, built around 1 person's habits instead of a product team's roadmap.

• Cost: no licence and no subscription for local playback. The Apple Music subscription stays, for discovery.
• Fit: only the features I use. The keywords I typed in Alfred for years (oa open and play, pa pause, ns next song) now drive Hifee.
• Risk: I own the maintenance. When macOS changes, the agent and I fix it. Nobody else will.
• Limit: Mac only, no phone app, no sync. My phone keeps Apple Music.

For technical people

Stack

Native Swift. SwiftUI for the views, AppKit where SwiftUI is too slow or too heavy. The library is a SQLite database, with FTS5 for search, so "royksopp" finds "Röyksopp". A 1-time script imported my Audirvana history: ratings, play counts, playlists and ReplayGain values.

Playback

• 1 AVAudioPlayerNode in an AVAudioEngine, with each track scheduled as a segment. The next track is scheduled 20 seconds before the end, which gives gapless playback and a seamless loop.
• Sample-rate switching through Core Audio (kAudioDevicePropertyNominalSampleRate). The gotcha: the output unit reports the new rate a moment after the device changes. Starting the engine before that left it silent. Hifee now waits until the output format matches.
• ReplayGain 2.0 at -18 LUFS, with a BS.1770 loudness meter for new tracks. At a gapless boundary, the gain change is a scheduled audio-unit parameter event, so the next track starts at its own level.
• FLAC tags are written in place when the padding allows, else to a copy that replaces the file atomically. Only the comment block changes; the audio is checked before the swap.

Apple Music

MusicKit needs 2 things for an app signed outside the App Store: the MusicKit service on the App ID, and an embedded provisioning profile that carries the application identifier. With the service alone, every request fails with developerTokenRequestFailed.

Sonos

The first version sent Home through AirPlay. That had a hard limit:

⚠️ WARNING: a third-party Mac app can't select AirPlay speakers by itself.

The AirPlay picker runs in a system service. Hifee could read the speakers I ticked, but it couldn't select them, and macOS dropped the selection when Hifee quit. So every restart meant ticking the speakers again. It also ruled out a voice command like "play Favourites at home".

So Home now talks to the Sonos speakers directly, over the same local API that Home Assistant uses (UPnP on port 1400). AirPlay is gone from Hifee:

• Rooms: Hifee finds the speakers on the network and groups the rooms I tick. 1 speaker leads and the others follow it in sync.
• Stream: Hifee runs its own small web server. The lead speaker downloads each track from it, and gets the next track in advance, so it moves on by itself.
• State: Hifee asks the lead speaker every 0.5 seconds what it plays. It sees the next track start, a pause from the Sonos app, or another app taking the speakers.
• Volume: 1 slider sets every room to the same level. The Sonos group volume keeps the differences between rooms instead, which isn't what I want.

What the speakers accept surprised me. I measured it before building:

FLAC would keep 24 bits, but the encoder that ships with macOS took 3 seconds for a 6-minute track. WAV renders at about 400 times real time. So Hifee sends 16-bit WAV, after ReplayGain and with dither, and resamples anything above 48 kHz. That's the same depth AirPlay used.

2 gotchas worth knowing:

• Old settings: the stored AirPlay volume was 100%, a stream level. Sent to Sonos, it would have put every speaker at full volume. Hifee ignores it, and the first time it takes the speakers' own level, at most 40.
• Local network: macOS asks whether an app may use the local network, and keeps 1 switch per copy of the app. Until both copies were allowed, every request failed with "The Internet connection appears to be offline". The system log said what it really was: "Local network prohibited".

Apple Music songs can't go to Sonos this way: Apple's copy protection blocks a re-stream. They stay on the desk.

Testing

The agent wrote a test harness that drives the real app from JSON scripts, on a copy of the database and a muted virtual audio device. It checks gapless transitions, rate switches, the focus loop, call and dictation pauses, memory, and renders every layout to images. For Home, it plays to a fake Sonos household of 3 rooms that runs inside the app, 20 times faster than real time, so a test never touches the real speakers. The screenshots in this note come from those renders.

1 small fix worth stealing: Alfred kept listing the build copies of the app. A folder whose name ends in .noindex is invisible to Spotlight, so the build now goes to build.noindex/.

Further reading

Audirvana

The player Hifee replaces

https://audirvana.com/

MusicKit

Apple's framework for Apple Music in apps

https://developer.apple.com/musickit/

• Apple Music
• Sonos, the speakers behind Home output
• LRCLIB, the open lyrics database
• Alfred, the launcher behind my keywords
• ReplayGain on Wikipedia
• The era of personal software is here, why I build my own software now