I believe that music has power, but what I’ve discovered recently is my old suggestion of making them sing is still viable, but in a new and unexpected way.
When my kids were little and angry with each other (or more likely me), I made them sing until everybody was happy.  This was typically a nighttime event because they were young and tired and slightly irrational little beings, so they’d go off on really small issues and at that moment, no conversation would work.
I sat in their rooms, encouraged them to sing a song with me and they never agreed right away, so I sang  ‘You Are My Sunshine’ all by myself.  I refused to leave until they were singing it with me and it only took about a minute before they were happy again.  My goal wasn’t  to resolve anything between them or me, I only wanted to lighten the mood enough to have a rational conversation, or at the very least have them go to bed happy and not all pissed off over something really small.
It worked every time.
It still works, but not in the same way.
Now if I ask them to sing they just get more angry. Â Of course I’m relentless about this and IÂ won’t stop singing until they at least stop throwing things at me. Â Eventually one of the sisters comes by to ask me to stop as well, and as a last resort they join forces to take me down. Â I eventually do go down, but never easily.
The downside to this is that they rarely agree to sing with me nowadays. The upside is that they see how working as a team can accomplish things for their greater good and by the end we’re all laughing (most of the time) and whatever was in the storm cloud has gone away and I can get some rest.  It may not make the issue go away for good, but it definitely makes us realize that we can deal with the small stuff in a small way, count blessings instead of keeping score, and gets them working together instead of at odds.
So yeah, I believe music has power, and sometimes in the weirdest ways.