The powers of the TC are vastly under appreciated. As a driver I had no idea personally. As Foxy says, they will pay heeled to behaviors on the road, with conviction or not. The driver I spoke to who handled his phone in the cab and got the 5 day suspension did not get a criminal conviction.
The TC can also take action on convictions too. One driver I know was on frount of the TC for a conviction for a non driving related crime. He got a verbal warning.
Back to the OP's post, I suspect conviction or not, holding or changing music on the lap the TC will suspend the licence for anywhere from 5 days to 4 weeks, hopefully with no other conditions.