Re:AMP is a fast, flexible, high-fidelity music player for macOS X, fully written in Swift. Re:Amp supports a lot of audio formats, custom interfaces called skins from classic Winamp. Re:Amp is freeware.
Music Widget is a remote app for Apple Music on macOS. It's a take on the original iTunes Widget introduced with Dashboard in Mac OS X 'Tiger' back in 2005. Music Widget looks extra sharp on retina displays because most of its interface is drawn in code.