Is this allowed? Small Forum Synchronizing Music To Videos

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I want to create a small website for a community of dance artists, we all enjoy creating dance video and the best platform for videos is youtube, but the biggest problem is the music we want to use in our video is copyrighted.

I want to create a website where users can upload links to their dance videos on youtube, and connect links to spotify urls with start/end times for the spotify song.

Other users would be able to watch the posts by seeing the embedded youtube video play along side the linked spotify track (from selected start to end).  

Of course, users would have to login/connect their personal spotify accounts, this would not be a free streaming service and without the connection/login they would only be able to see the posted youtube videos.

But once a user has connected their spotify account the website would be able to use APIs to start/stop spotify songs in an embedded player to synchronize with embedded youtube videos.

Would this be possible?

Is it violating any kind of ToS?

Are the necessarily APIs available to do this?

[Ximzend]

No. It's prohibited by two rules:

Spotify Developer Policy

III. Some prohibited applications

5. Do not create any product or service which is integrated with streams or content from another service.

6. Do not synchronize any sound recordings with any visual media, including any advertising, film, television program, slideshow, video, or similar content.