Sing along if you know this one. It is a familiar theme. Market dominance is so intoxicating that an incumbent — China’s Tencent Music, for example — goes a little too far. A killjoy, in this case an anti-trust regulator, inevitably comes along planning to stop the fun.

The New York-listed stock has dropped nearly 4 per cent following reports a competition investigation had begun. Slowing online sales mean shares are already down a quarter over six months.

Tencent Music holds 80 per cent of China’s music-streaming market. It makes a lot of money from karaoke and has ironclad partnerships with big labels such as Sony, Warner and Universal Music. The group has exclusive licensing rights to 20m songs. Controlling shareholder Tencent plans to a buy a 10 per cent stake in Universal Music. This would fortify the stronghold further.