I often find that the playlists I want are on Spotify when I usually use Apple Music. When I was looking for apps that could move the playlists, many of them had subscriptions attached to them and I didn't want another subscription.

So I created an app that lets you shift songs between Spotify and Apple Music and back! You can get the app here: https://apps.apple.com/us/app/playlist-shift/id6475181778. You can see a demo of how it works here: https://www.youtube.com/shorts/UrRpGpv_g64

I also recently added a feature that is useful if you need to repeatedly shift playlists. You can save those shifts and complete them with 1 tap. You can see a demo of that here: https://www.youtube.com/shorts/xdP59Uaduf8