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One side of my first valve slide feels "scratchy". I don't know how to describe it but it isn't as smooth as the other side. Any remedies for this other than frequent greasing?

1) Take a rod and cloth to swab out the inside of the offending outer tube(s).
2) Wipe of the offending inner tube(s).
3) Feel all around the offending inner tube(s) to determine if it is smooth or not. If you feel something protruding, you sand it down and then buff it smooth. Try the slide again. Proceed to next step if necessary.
4) If inner tube feels fine, use tubing expander adjusted to just the right size and gently push into the offending outer tubing and feel for a particular spot where there is more resistance. Typically that will be at a brace soldered onto the tube. It will also tell you where there is a dent in the tube. Use the expander to stretch out the tubing at that spot. Clean everything and try the slide again. If still not up to your expectations, prodceed to next step.
5) Clean the inner and outer slide tubes. If slide works but is still not perfect enough for you, lapp the slide tubes using a non-imbedding water based lapping compound. Continue to lapp the individual slide tube until it fells and sounds as great as the non offending slide tube. Once it finally meets your seal of approval, take apart the entire horn, wash out the slide tube area with a degreaser, then wash out the entire horn again with grease fighting Dawn Dish detergent. Lubricate and reassemble the the offending slide with preferred lubricant and decide that it is good enough or lapp it in some more which means washing everything out again. Reassemble the entire horn once you decide the slide is good enough.

There you go. If the slide assembly works well enough but there is still some noise left after you have spent 3-5 hours doing all this work or paying a repairman shop rate for his time, you will most likely tell yourself, "To hell with it. Nobody is going to hear this little noise but me." However......
If even the faintest of sound only heard when you close your eyes and cock your ear to the side to listen still bothers you, you were born a trombonist and took up the tuba by mistake. In which case ignore everything above and get a life instead.

This procedure does not address parallel issues.

Matt Walters wrote: If even the faintest of sound only heard when you close your eyes and cock your ear to the side to listen still bothers you, you were born a trombonist

.

I want to be a trombonist when I grow up.

"I'm sorry, son, you can't do both."