Hello wastehead. I ditto. However, when you say "soundproof", what exactly are you trying to do? Without knowing what your circumstances are, no one can help you much. For instance, it's a no brainer that you are trying to keep the sound of drums from "escaping"

The trouble is, you have THREE devils.
Impact sound
Low Frequency
High SPL(sound pressure level) in other words....loud.
You need to understand it is true that "soundproofing" is expensive. But what tells you that you need it? D Complaints? Possible eviction? A warning?
WHO and WHAT are you trying isolate the drums from? Where are they in relationship to the "playing room" . Is this a basement? Or a garden shed? Or a garage? A bedroom? Tell us all you can and we may be able to help you define and do to help the situation to a degree. There ARE things you can do, to reduce transmission of the impact noise via the structure. But we need to know some things.
Like what the floor is made of. Any rooms adjacent to it? When you say finished ceiling, what kind of ceiling? Is there a floor above this ceiling or an attic? If floor, what kind of floor? Is it a bedroom or other? Any neighbors that you are concerned about? if so, how far are they? If not a basement, what is the exterior of the house or room sheithed in?
Well, these will do for a start. Once we know some things, we can better help you define what it is you have to do. Only then will you know what it will cost to reach your isolation goals. Thats usually when reality checks have the most impact on your decisions. Compromise is the usual recourse. I can tell you this. Under the best of circumstances, to isolate drums from an adjacent room can be very expensive, difficult, demanding, and uncaring should you make a mistake, and sometimes, illegal if you do certain things without a Building Permit. Under the worst circumstances, it can be relatively impossible unless you are Bill Gates

But like I said, it's all relative to YOUR circumstances and budget.
fitZ