OK, one of my characters is a minor practioner who uses music as his medium. He has a lot of enchanted music instruments and focus items. We played an adventure last night and he asked about an enchanted guitar case to hold all his items and equipment in. He had tried to make something but was not sure and in the middle of the game I was not going to stop and try to build magic items. It was not and will not be a huge plot device to any story so I let him use it last night. It really is just a way for him to justify carring all this around with him.
So my question is - how would you stat something up like this? He and I quickly decided on an item that has the Aspect 'Bigger than it Looks' on it and just say the it is big enough to hold his 4-5 instruments and some focus items. But given time and following the rules as written, how would one do this?