Minecraft wiki entry for Sound_directory, associated text: ambient: Ambiance and rain/thunder
damage: Sounds of the player taking damage
dig: Breaking blocks
fire: Fire sounds
firework: Fireworks sound effects
liquids: Sounds made by liquids such as water and lava
minecart: Sounds created by moving minecarts
mob: Mob sounds
music: Background music by C418
random: Various sound effects from eating to explosions
records: Music on the record discs found
step: Footsteps
tile: Pistons