Answer:
rub me and a genie might appear
I am an instrument capable of making numerous sound but cannot be touched or seen.
I am pronounced as one letter written with three. I come in blue black brown or grey. Reverse me and I read the same either way.
My first is in some but not in all. My second is in tiny but not in tall. My third in little but no in big. My fourth in port but not in pig. My whole is made in nature's way. For clothing rugs used every day.
I begin and have no end. Eventually I will be the end of all that has begun.
When someone uses this acronym, you know you've got to pick up the pace