Answer:
I am an instrument you can hear but cannot touch or see. What am I?
I begin your sentences.
I am not very commonly found! Only in some rainforest! I have an odd number of toes! I'm very lazy and hang upside down! What am I?
People need me, yet they give me away every day. What am I?
Fatherless and Motherless, born without sin. Roared when it entered the world, And never spoke again.
No matter how little or how much you use me, you change me every month.