Our extension is free and generally doesn't require any paid subscriptions.

Oops! We've accidentally introduced an auth bug in version 3.1.5. This version is now disabled and we advise updating to the latest version. Our apologies!

The extension does not require a sign-up. You can use it without an API token. The API token field is for people with an active subscription. The free trial is for our API product and shouldn’t be used in the extension; the extension works without an API account and is completely free.

Unfortunately, many tracks are not officially published, and we can't identify them :(
In our DB, we only have songs available to us through our partners in the music industry, so we don't yet have lots of music.

Can you please share more info? What is your browser and OS version and what was the website? The extension works on, e.g., YouTube, just fine for us