Hi all, I'm new here, thanks for this great forum! I have a French horn I acquired new in 1963, played a lot for many years. About 17 years ago, had to stop playing for a while. Restarted about two years ago, and am slowly getting my chops back. When I restarted, I noticed the horn was playing very sharp, I had to keep the main tuning slide almost all the way out. So far that it sometimes fell out . This is about an inch farther out that it had always played, which is a lot for this horn. My friends tried it and got the same result. I had washed and snaked it out when I restarted. Then washed and cleaned it out (I think) using a snake and a lot of warm water again, about six months later. After that second cleanout, it was a little less sharp, though the slide was still out like 3/4" or so more than in the good old days. I suspect that over the 15 years I didn't play it, some crud dried hard on the inside of the horn, reducing its effective volume and making it go sharp. The first cleanout didn't penetrate the superhard crud, and it stayed in place. The second cleanout was after six months of playing, and some of the crud may have softened a little and the snake brushed it out. But I suspect there's still some in there. I'm about to clean and snake it out again. My question is, is there anything I can use (cleaning fluid or soap or dishwashing liquid or whatever) that will help get that crud out of there without damaging the horn? Is there any cleaning fluid specifically designed for brass instruments? I can let it soak a long time (days) if needed. It's a Mirafone "Siegfried" model double horn, gold-brass alloy, they made a few of them back in the late 50s and early 60s, yes that's how the company name is spelled on it. Ring around the bell, engraved valve caps a la Alexander (but they are original Mirafone) still has the original hard-rubber "corks" in the valves (quite a novelty in 1963), it's a much better horn than I am a player. Thanx all!