You actually guess the tempo of your favorite songs. Being mauled by a drum is a normal part of life. Your uniform fits. You call the band bus driver by their first name. You can sight-read.
Reeds taste good.
You can relate to more than 15 of these things. You subconsciously start practicing with a pencil. Numbers past 8 aren't important. Letters past G are no longer important. Everybody fights like family.