Breath and Brass

What it is: The principle that every brass line is constrained by the player's air supply and the embouchure's endurance. Brass demands more recovery than woodwinds because the lips fatigue independently of the lungs — you can have plenty of air left and still have lips too tired to play another high note.

What it sounds like: When you ignore brass breath/embouchure: cracked notes, splats, attack failures on what should be the climactic high entrance. When you respect it: brass entrances that arrive fresh and confident.

When to apply it: Every time you write for brass, and especially:

Sustained high passages — anything above the staff for more than four bars
Tutti exposed entries — first notes after long rest are vulnerable
Final climaxes — the player needs energy, not exhaustion, at the moment of arrival

Three Rules

Cushion every high entry. Don't make a high climactic note the player's first note after silence — give them at least a bar to settle the embouchure. The exception is dramatic effect (Strauss Don Juan opening), but that's a heroic gesture, not a default.
Recovery bars are real. After sustained writing above the staff, give the section a bar or two of rest — not just a quarter rest. Stagger releases so the texture continues while individual players recover.
Lower writing is cheaper. Middle-register brass writing is endurance-affordable; high writing is expensive. Budget your high moments — they should be events, not the default tessitura.

Tip: Show the score to a brass player before the rehearsal. They will spot endurance problems instantly that a non-brass-playing composer won't see. The most common note: "this whole line lives in the high register — can we drop the middle eight bars an octave so I make it to the end?"

For the parallel principle in winds (and the shared concepts), see Breath and Phrasing.