Simplify the following text for a Grade 6 native English-speaking person.
Original: These pieces are noted for being dark and mysterious ( a characteristic of this key ) , as shown even in the later jazz compositions '' ` Round Midnight '' and `` Take Five '' , which are also in the key .
Simplified: These pieces are noted for being dark and mysterious , a mood this key has . This mood is shown even in the later jazz music '' ` Round Midnight '' and `` Take Five '' , which are also in the key .