Brass instruments are made of metal. The sound is produced by the player placing their lips against a mouthpiece and making a sound like a raspberry (or buzzing) into the mouthpiece.
It is this vibration which creates the sound. Brass instruments have a very distinctive sound which you will hear in the Minutes.
Where are these instruments being played?
Is anyone else nearby?
How can you tell?
How are they making their sounds?
Describe how the vibrations were produced and then travelled to the microphone.