Excellent. Now I know what Sing-Sing is. You see, I was listening to a CD from Cap. Kiwi's vast Hip-Hop collection today (Wu Tang - Forever), and one bloke says:

I sing a song from Sing-Sing, sippin on ginseng

I wondered what Sing-Sing might be, now I know!
As for the 'up the river' biz.. well, my guess was based on the fact that I learnt it from a real Cockney bloke.

BTW. a friend of mine comes from Baden-Baden.