The Infernal Devices question

Hello, i hope someone may be able to help me remember a set of books i read a while back. I think there were 3 out at the time.
The protagonist were brother and sister being raised by their aunt. She was rather stern and made them keep a clean room and were home schooled. If something was left out it disappeared. It turns out they are the children of gods or supernatural parents. They receive a gift of a violin or fiddle for him, i believe the sister got a bow. They are being sought by other gods, or demi gods and these instruments help them. At some point they are sent to a school that is for children like them (Supernatural) and together they fight the powers, i think i remember them going to hades. the aunt controls time or fate. I have been unsuccessful in searching all the YA books here for the series. hopefully this is enough information that some one will know what they are called.

Thanks all