Due to Spotify's recent changes related to their API access, I've made the decision to discontinue this app. My primary goal with this app was always about making it possible to open Spotify links directly in Apple Music, and it doesn't make much sense to pay for a Spotify subscription that I wouldn't use for anything else.
I got tired of manually searching for music in Apple Music when one of my friends sent me a link to something in Spotify, so I created Euphony. It’s a web extension for Safari that, once configured, automatically opens Spotify links in Apple Music or vice versa.
First, go launch the Euphony app, it should be in your Applications folder. This ensures the extension shows up in Safari.
Next, open the Extensions pane in Safari's preferences and enable the Euphony extension by checking the box next to it.
After enabling the extension, click the "Edit Websites…" button. Then change all of the options to "Allow" for each site. This lets Euphony do its thing without asking you every time to access the sites.
Finally, close the Preferences window and click the Euphony icon in the toolbar. Here you can set your preferences of what links should be converted. Fair warning, if you enable both you might end up in a small loop.
First, go launch the Euphony app, it should be on your home screen somewhere. This makes sure the extension shows up in Safari.
Next, open the Settings app and tap on the Safari settings. Find the Extensions settings and tap on it. Then tap on Euphony in the list of extensions and toggle it on. While you're there, change all of the permissions to "Allow" for each site. This lets Euphony do its thing without asking you every time to access the sites.
Finally, open Safari and load any site. Tap on the 
button, then tap on Euphony to open the extension preferences. This will let you set if you'd like Euphony to automatically convert Spotify links.
There are a couple known issues with Euphony on iOS right now that I’m not sure if I can resolve:
Euphony does not collect, store, or transmit any personal information. The extension makes one call to my server to get a valid Apple Music token. I’m not logging anything about that server call.
If you have any questions, email me.