Peter Head was puzzled about whether a horn needs breaking in.
It is important to do an effective job of breaking in a horn. Not only will you achieve better playing results, but breaking in, when conducted in a sensitive and patient manner, will result in intense psychological bonding between you and your horn.
Here is how to break in a new horn. After taking the horn out of its case, you open a book of your favorite etudes on the floor, not too close. Then you practice a while. Once you notice that the horn has deposited condensation on the floor, you stop playing, look sternly at the horn, and say, "Bad horn!" Then you carry the horn to the book of etudes, and put it down on top.
After a while, your horn will catch on. But do be patient. Your new horn will not respond well to threats. I have never understood players who punish their horns by swatting them with a rolled up newpaper. I have reported several such players to the SPCH.
When my horn has been especially good, I like to reward it with a yummy little horn biscuit. (My horn's taste in baking goods is similar to mine.)
Used instruments may require special attention if they have been broken in poorly. Instruments formerly used in marching bands, for example, prefer to be let outside periodically. Other instruments, especially natural horns, prefer to use a box of horn litter, which is manufactured from absorbent Kopprasch Krums.
Good luck breaking in your horn. Just be glad you aren't breaking in a trombone. In fact, trombones are nearly as hard to break in as trombonists.
Gotta go,
Cabbage