Baby Grand Piano Mimic

Shapechanger.
The mimic can use its action to polymorph into an inanimate object (such as a baby grand piano) or back into its true, amorphous form. While in object form, it is indistinguishable from the real thing.

False Appearance (Object Form Only).
While the mimic remains motionless in its piano form, it is indistinguishable from a normal baby grand piano. A creature that plays it must succeed on a DC 15 Wisdom (Perception) check to notice something is wrong before it attacks. Advantage to the PC if the PC is a bard or has performance skills.

Adhesive (Object Form Only).
The mimic adheres to anything that touches it. A creature grappled by the mimic is also restrained, and creatures touching it are considered grappled unless they succeed on a DC 13 Strength check.

Pseudopod. Melee Weapon Attack: +5 to hit, reach 5 ft., one target.
Hit: 7 (1d8 + 3) bludgeoning damage. If in object form, the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and the mimic can’t use this pseudopod on another target.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target.
Hit: 14 (2d8 + 3) piercing damage plus 4 (1d8) acid damage.

Discordant Chord (Recharge 5–6).
The mimic emits an unholy piano chord, magically resonating through its body. Each creature within 15 feet must make a DC 13 Constitution saving throw or take 13 (3d8) thunder damage and be deafened until the end of its next turn. On a successful save, they take half damage and are not deafened.

Instrumental Slam.
The mimic can slam its “lid” down with surprising force, dealing bludgeoning damage and trapping limbs. (3d6 +6)

Shape-Shift. The mimic shape-shifts to resemble a Medium or Small object while retaining its game statistics, or it returns to its true blob form. Any equipment it is wearing or carrying isn’t transformed.