Look out! Kobolds! Wait a minute... what’s that sound? Is it singing? Quick nail down the fighter! Dang it! The cleric is running for the hills! Harpy! Harpy! Throw this adventure in as a way for lower level characters to take a bypass around a much more challenging creature, or as a a way to connect two levels together.
Enough adventure for an evening or two for 1st-2nd level characters