Make a riddle that is hard

I am full of keys, yet I cannot open any locks,

A puzzle of secrets, like a paradox.
Sometimes I reveal, sometimes I hide,
With intricate patterns, I can easily slide.

What am I?

What the answer

The answer to the riddle is a piano. A piano is full of keys but cannot open any locks. It is a musical instrument that holds many musical secrets and can reveal or hide emotions through its intricate patterns of notes. The keys on a piano also slide easily when played.

Sure! Here's a riddle for you:

I speak without a mouth and hear without ears. I have no body, but I come alive with wind. What am I?

Can you guess the answer?