OK, I’ve had a look at your patch.
Here’s the answer : in MaxForLive it is not possible to observe if a clip slot is playing.
You can only access the property “is_playing” with a “get” message (and it only works with clip slots of Group Tracks).
If you really need to know if a clip slot is playing using “observe”, then you can use the property “playing_status”.
But this, too, can only be used with clip slots of a Group Track.
If the clip slot you need to observe is not inside a Group Track, then you can observe the clip playing status (instead of the clip slot), or you can know if the clip is playing using a “get” message.
Please don’t hesitate to tell me if this is not clear enough, and, if you’re not familiar with it, I suggest that you explore this page :
https://docs.cycling74.com/max7/vignettes/live_object_model
