I know this is a long shot as you can't hear from your Pc but the engine on the 600ss has a ringing sound at tick over it does not sound terminal and fell it may be how they are as when revved or on the road it is quiet and runs well sorry for the poor description I think it may be the desmo valves working ?
I have to say it does not sound worrying and in my gut feeling it makes it sound better ????? bit wierd eh!
My dad's 900ss has a ringing sound which is caused by loose rivets on his exhaust cans. Might be worth a check
Mine does it at approx 2500 rpm when blipping the throttle as the revs fall............can't find out what it is..............but it has done it since I got the bike four years ago, so I ignore it. It might even be that the silicon 'plugs' between the barrel fins have all fallen out.......