Legality question: Removing vocals from a track for singing app

[SomebodyThatIUsedToN]

For an app idea I am developing I was wondering, whether it was allowed by spotify to let users connect to spotify through the app, stream music they like and have our app remove the vocals for the user to sing along to the song. The background would be a singing teaching app, so the purpose is not karaoke, but singing pedagogy.

The developer guidelines leave me unsure regarding this point. Thank you for any help 🙂

[Ximzend]

At the Getting Started with Web Playback SDK page, you can read:

Important policy notes

Keep audio content in its original form

The Spotify Platform can not be used to develop applications that alter Spotify Content.

More information