They can be both high and low pitch. There are brass instruments
that are considered "high voices" like trumpets, there are brass
instruments that are considered "middle voices" like french horns,
and then there are brass instruments that are considered "low
voices" like trombones, euphoniums, and tubas. All brass
instruments have a pretty large range of pitches they can play
depending on how good the player is, so the pitches can greatly
vary.