Music Router catches your Mac Play key before it opens Music

Pressing Play ought to mean playing something you chose. On an idle Mac, it can instead mean welcoming Music back onto the screen. Music Router puts a small menu bar utility between the media key and that assumption, giving a keyboard button a less presumptuous interpretation.

The project’s README describes two different fixes because macOS has more than one way to summon Music. For keyboard events, it intercepts play, pause, next and previous before the default handler sees them. The maintainer calls the result “no flash, no launch-then-kill”. Blocking the invitation early is tidier than escorting the app out after it has already arrived.

The decision depends on what is currently playing. Music Router checks the system’s Now Playing session. If a native player or a browser tab already owns that session, the event passes through untouched and macOS handles it normally. That keeps the utility from treating every press of Play as a request to start its favorite app over whatever you were already hearing.

When nothing is playing, the key can launch a replacement selected in its menu. The menu offers installed players, a custom application, a web address, or Block Only. Your choice. Scriptable native players can receive playback commands; web destinations and applications without that interface fall back to opening. A web page appearing is therefore a different promise from a song beginning automatically.

AirPlay speaker selection, iPhone Handoff and Siri requests do not arrive as keyboard events. For those, the utility watches application launches and immediately terminates an unwanted Music process. The README calls this a “real, permanent limitation”. An app that explains where its elegant interception stops is easier to judge than one that calls every rough edge an upcoming feature.

The permissions are consequential to setup. Its documentation requires both Input Monitoring and Accessibility for the key interception. A checked box for only one can leave the event tap unavailable. The app is ad-hoc signed rather than notarized, and changes to signing identity can leave permissions needing approval again. A silent Play key is no reason to assume your keyboard has developed a musical grudge.

Behind the menu, a long-running media-control process watches playback state. The keypress reads cached state instead of spawning a subprocess each time, according to the implementation notes. That is a sensible place for the work: a button you tap repeatedly should not need to conduct a fresh investigation of the entire desktop on every press.

This is a narrowly useful fix for somebody who already has a preferred player. Block Only suits the person who wants Music to stay closed; choosing a replacement suits the person who expects Play to start a particular service. The unresolved compromise is still there on the non-keyboard paths, where Music has to launch before the guard can close it.

Music has lost the opening act.