While it's not to the same degree as a string instrument, a lot of brass instruments require the player to create the pitch. They might have 3 keys with which to play all their notes, so the sounds aren't predetermined, they need to be pitched by the player.

And to an even lesser degree all instruments require the player to pitch them properly, because even with keys and buttons, they still need to be fine tuned while they are played. Many woodwinds get sharp as the scale rises, so the player needs to know to pitch down a little, or certain notes might always play flat, so the player needs to pitch up.