I have heard in my travels that one can clean tin/lead organ pipes
by placing them in a bath tub of water and using "Spic 'n Span" and
letting them soak a while. I never tried it but it is worth a try.
I have no specs on how much Spic 'n Span to use nor what a "while" is.

Let us know what method you used and how successful you were.

Andy LaTorre