Some brass instrument manufacturers make a feature of the shape of the various slides - some have a semi-circular wrap, other more semi-elliptical. Some have a tight wrap (the two legs of the slide are close together) or an open wrap (legs further apart).
My question is - what effect do the shape and tightness of the tubing wrap have on the sound and instrument playing response?
I'm asking because some manufacturer claims sound like voodoo to me - I'm wondering whether there are good physics reasons for choosing the shape of an instrument, or whether the choice of shape is mostly based on cosmetics and having an instrument that isn't tiring to hold, e.g. the centre of gravity is in a place where the instrument doesn't tip forward or backward when you're playing it.