Is there a shortcut for

var repeatMode: @Player.RepeatMode Int
        get() {
            return player.repeatMode
        }
        set(value) {
            player.repeatMode = value
        }

What about this?

var repeatMode2: @Player.RepeatMode Int by player::repeatMode

Neato

so tear-offs are instances of 'Delegate'!? Or just made into one if necessary? Or can 'by' handle Delegates and tear-offs?

It looks like kotlin compiler handles such cases. I wrote a simple example and it was optimised to good old getter and setter invokations (on JVM at least):