The best alternatives to OneSong are Converse Sample Library, Ditty, and Songshare. If these 3 options don't work for you, we've listed a few more alternatives below.
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Songshare for macOS is the fastest way to share what's playing. Songshare lets you share the Spotify or Apple Music link to your current song, regardless which app you're listening on. No account setup required. Just click the icon in your status bar to grab either the Spotify or iTunes share link! Demonstration: https://vimeo.com/259281301