SynthesisPrivacy Notice
Effective 4 October 2026
Synthesis is a music player for Mac, iPad and iPhone. It plays your Plex library, can show Apple Music alongside it and
fills its pages with information from the Synthesis service: credits, artist biographies, album notes and related
music. This notice explains what personal data that involves, why we use it and what you can do about it. It covers
the Synthesis apps, the Synthesis service (api.synthesis.map-territory.net) and this website.
The short version: Synthesis has no accounts and no ads, and it doesn’t track you. To work out who played on your records and what to play next, the app sends a list of your Plex music and, unless you turn it off, your Plex plays to the Synthesis service. They’re stored under a random ID made on your device, never with your name, email or Plex account, and you can delete them at any time in the app. Your Apple Music listening stays on your device.
Who Is Responsible
The controller of your personal data under the General Data Protection Regulation (GDPR) is:
Map + Territory
The Hague, the Netherlands
Registered with the Dutch Chamber of Commerce (KvK) under 89412869
Email: bastiaan@map-territory.net
In this notice “we” and “us” mean that controller. We haven’t appointed a data protection officer; we aren’t required to. Write to the email address above about anything in this notice.
What Stays on Your Device
Most of what Synthesis knows about you never leaves your devices:
- Your Plex sign-in. The app signs in to Plex directly and keeps the token in your device’s Keychain. We never see it, and we never see your Plex account name, email or password.
- Your Plex server. The app talks to your Plex server directly. Server names and addresses, machine identifiers and the paths of your files stay on the device.
- Your Apple Music data. When you connect Apple Music, the app reads your recently played music, saved albums and Apple Music library on the device, keeps them in a local cache and never sends them to us. Plays of Apple Music songs are never sent either.
- Your settings and lists. Pins, sidebar order, saved searches, Listen Later and similar settings are kept on the device and, when you use iCloud, synced through your own private iCloud database. That database belongs to your Apple account; we can’t read it.
- Saved answers. The information the service last gave the app, including what it worked out from your library, is kept in a local cache on the device so pages and Home still show it when the service can’t be reached. It stays there until the service gives a newer answer, you clear the cache in Settings › Storage, or you delete your data. Delete Your Data removes the saved answers about your library too.
What the Synthesis Service Receives
Requests for Music Information
When you open an artist, album or person page, the app asks the Synthesis service for information about it. A request carries:
- the subject: a MusicBrainz ID, or a name, title or barcode to look one up. One subject per request; these requests never carry your library or your plays.
- a random install ID made by the app when it’s first opened, used to apply fair-use limits per installation.
- App Attest data (see below).
- your IP address, which reaches Cloudflare, our network provider, as with any internet connection.
If you add your own fanart.tv personal API key in Settings, the app sends it with requests for artist images; the service passes it on to fanart.tv and doesn’t store or log it.
We don’t keep these requests. Our server logs record the kind of request, its status, size and duration and a request number, but not your IP address, install ID, random ID or what you asked about. Rate-limit counters use salted hashes of the IP address and install ID and are kept in memory for a few minutes.
Your Library List
If you use Synthesis with a Plex library, the app sends the service a list of that library, and keeps it up to date. The service uses it to show who played on your records, which albums you have and which you don’t, the versions you own and what to play next. This is part of how Synthesis works with Plex: to stop sending it, turn off Plex in the app and use Synthesis with Apple Music only.
What the list contains: artists, albums and songs with their titles and names, years and release dates, album types, disc and track numbers, lengths, the IDs Plex gives them (including MusicBrainz IDs where Plex has them), ISRC codes where Plex has them, audio format (codec, bit depth, sample rate), when you added them, and how often you played them, when you last played them and how you rated them.
What it never contains: your name, email, Plex account or user names, file paths or stream addresses, server names, addresses or machine identifiers, library section names, Plex sign-in tokens, your playlists, collections or genre and mood tags, artwork, device names or IP addresses.
Your Plex Plays
Unless you turn off Send Plex plays in Settings, the app also sends the plays from your Plex history: for each play, its entry number in your Plex history, the song’s Plex ID and the time you played it. Only the plays of the signed-in Plex account are sent, never those of other people on the same server, and never the device or app you played on. The service uses them for recommendations on Home. When you turn the switch off, the app stops sending plays and the service deletes the ones it has and the play counts made from them.
Your Choices for Recommendations
So that Home’s recommendations respect them, the app also sends your Never Suggest list and the artists you follow: for each, its MusicBrainz ID, or its name where it has none, and the name as shown. They’re stored with your library list under your random ID and deleted with it.
Your Random ID
Your library list and plays are stored under a random ID, not under your name or any account. The app makes a random secret on your device and keeps it in your Keychain; with iCloud Keychain on, your Mac, iPad and iPhone share it, so they count as one listener. The service stores only a one-way fingerprint (a SHA-256 hash) of the secret. Settings shows the first 12 characters of that fingerprint as your Random ID, so you can quote it if you write to us.
This data is pseudonymous: we can’t tell who you are from it. It’s still personal data under the GDPR, because it’s about you, and this notice treats it that way.
App Attest
To keep the service for genuine Synthesis installations, the app uses Apple’s App Attest. Your device makes a key in its secure hardware and Apple certifies that the key belongs to an unmodified copy of Synthesis; each request is signed with it. The service stores the key’s ID and public key, Apple’s certificate and receipt, the operating system and app version, a request counter and a hash of the install ID. Before your library list is first sent, your device’s key is linked to your random ID, so that only your devices can read or change your data. App Attest doesn’t give us your name, Apple account or device serial number.
Emails
If you write to us, we receive your email address, your message and anything you include, such as your Random ID.
Why We Use It and Our Legal Basis
The GDPR allows us to use personal data only on a legal basis (Article 6). Ours, per purpose:
| Purpose | Data | Legal basis |
|---|---|---|
| Show the information you open: credits, biographies, notes, related music | Requests, install ID | Performance of a contract (Art. 6(1)(b)): it’s what you use the app for, under the Terms |
| Library features: who played on your records, what you own, versions, gaps, recommendations from your library | Library list, Never Suggest list and follows, random ID | Performance of a contract (Art. 6(1)(b)) |
| Recommendations from your listening | Plex plays | Our legitimate interest (Art. 6(1)(f)) in recommendations that follow what you actually play. The data is pseudonymous and you can turn it off at any time with Send Plex plays |
| Keep the service working and protect it from abuse and automated scraping | App Attest data, install ID, IP address (hashed, in memory) | Our legitimate interest (Art. 6(1)(f)) in a secure service and a fair share of its capacity for every user |
| Backups, so data isn’t lost in a failure | Everything the service stores | Our legitimate interest (Art. 6(1)(f)) in a reliable service |
| Answer your email and your requests under the GDPR | Your email and what it contains | Legal obligation (Art. 6(1)(c)) for GDPR requests; otherwise our legitimate interest (Art. 6(1)(f)) in answering you |
| Deliver this website | IP address, browser request | Our legitimate interest (Art. 6(1)(f)) in showing the site to visitors |
Where we rely on legitimate interest, we’ve weighed it against your interests: the data is pseudonymous, limited to what the feature needs, never shared for anyone else’s purposes and easy to switch off or delete. You can object at any time (see Your Rights).
The random secret and the install ID are stored on your device because the service you asked for can’t work without them; that is why the app doesn’t ask for separate consent to store them.
We don’t use your data for advertising, we don’t sell or rent it, we don’t combine it with data from other companies and we don’t track you across apps or websites. Recommendations are suggestions in the app; we make no decisions about you that have legal or similarly significant effects (Art. 22).
Who Else Handles It
We use these service providers. They process data only on our instructions, under data processing agreements (Art. 28):
| Provider | What they do | Where |
|---|---|---|
| Contabo GmbH, Munich, Germany | Hosts the server that runs the Synthesis service and stores its data | Germany (EU) |
| Cloudflare, Inc., United States | The network in front of the service and this website (delivery, caching, protection against attacks, the secure tunnel to our server), hosting of this website, and storage of encrypted backups (Cloudflare R2) | Worldwide edge network, including outside the EU. Cloudflare chooses where backups are stored, which may be outside the EU |
Transfers outside the EU. Cloudflare is a US company and its network serves traffic from data centers around the world, including outside the European Economic Area; our backups in Cloudflare R2 may also be stored outside it. For transfers to Cloudflare we rely on its certification under the EU-U.S. Data Privacy Framework and on the Standard Contractual Clauses in its data processing addendum.
Who doesn’t get your data. The service writes its album notes, artist biographies and related-music reasons with an AI model from OpenAI. It sends the model public facts about the music only (from MusicBrainz, Wikidata and Wikipedia), never your library, your plays, your random ID or anything else about you. The same goes for the public sources the service reads from (MusicBrainz, ListenBrainz, Wikidata, Wikipedia, Wikimedia Commons, Cover Art Archive, fanart.tv, Discogs data and the Apple Music catalog): the service asks them about music, never about you.
We may disclose data when the law requires it, for example to comply with a court order, and only as far as required.
Plex and Apple. Plex, Apple Music, iCloud, the App Store and TestFlight are services you use directly, under their own terms and privacy policies. What you share with them is between you and them, and we aren’t responsible for it. If you choose to share crash reports or app analytics with developers in your device’s settings, Apple passes them to us without your identity.
How Long We Keep It
| Data | How long |
|---|---|
| Your library list and what the service works out from it | While you use Synthesis. If no device with your random ID contacts the service for 180 days, everything stored under it is deleted |
| Individual Plex plays | 400 days. Older plays are then combined into play counts per artist and per album, which are kept with your library list and deleted with it |
| Plays after you turn off Send Plex plays | Deleted when you turn it off, with the play counts made from them |
| Your Never Suggest list and follows | While you use Synthesis, with your library list |
| Uploads in progress | 24 hours |
| App Attest key records | While your installation uses the key. They’re linked to your random ID only until you delete your data or it’s deleted after 180 days without contact |
| Rate-limit counters | A few minutes, in memory only |
| Server logs | Rotated by size; they contain no IP addresses, install IDs or random IDs |
| Backups | Deleted data can remain in backups for up to 35 days, then the backup is deleted |
| Emails | As long as needed to answer you and keep a record of GDPR requests, at most two years |
Your Rights
Under the GDPR you have the right to:
- access the personal data we hold about you and get a copy;
- rectification of data that is wrong (the app corrects your library list on its next sync);
- erasure: in the app, open Settings and choose Delete Your Data. This deletes your library list, plays and everything worked out from them at once, and makes a new random ID. If Plex stays on, the app sends your library again under the new ID; to stop that, turn off Plex in the app;
- restriction of processing while a question about your data is being settled;
- data portability: a copy of the data you gave us, in a common machine-readable format;
- object to processing based on legitimate interest. For plays, turning off Send Plex plays does this at once;
- complain to a supervisory authority: in the Netherlands the Autoriteit Persoonsgegevens, or the authority where you live or work.
To use a right we can’t serve in the app, email us at bastiaan@map-territory.net and include the Random ID from Settings. We don’t know who you are, so the Random ID is how we find your data; without it we may not be able to (Art. 11). We answer within one month, free of charge.
Security
Connections to the service and this website are encrypted (HTTPS). The server accepts no direct connections from the internet: traffic reaches it only through Cloudflare’s secure tunnel, and administration uses key-based SSH. The service stores only a hash of your random secret, accepts personal requests only from App Attest keys enrolled to your random ID and never caches them on the network. Backups are encrypted at rest.
This Website
This website has no cookies, no scripts, no analytics and no third-party content; its fonts are served from this site. Cloudflare delivers it and, like any web host, processes your IP address and the details of your request to do so and to protect the site from attacks. Browsers may also send Cloudflare reports of failed connections (Network Error Logging). We haven’t turned on any visitor logging or analytics.
Children
Synthesis isn’t meant for children under 16. Because we don’t know who our users are, we can’t tell a child’s data from anyone else’s; a parent or guardian can delete it with Delete Your Data or by writing to us with the Random ID.
Changes to This Notice
When we change this notice, we publish the new version here with a new effective date. If a change affects what we collect or why, the app tells you before it takes effect.
Contact
Map + Territory
The Hague, the Netherlands
bastiaan@map-territory.net