Need to know boundaries first and then council issues before going to far.

Cheapest thing to do would be to paint the doors put a bit of timber benchtop from Bunnings and perhaps mirror the back panel, but where's the Bar Fridge going or are you planning a bigger fridge nest to this. As Louie suggested it might be better to get rid of the old as there's no place for a much needed Bar Fridge, A Barn door of whatever style suits you would work well, you can pick up second hand doors with character for this. Then again some Bunnings timber benchtop , (Mel) fitted & supported by beams screwed into the rear and sides of the nook and hidden by a strip across the front as your bench top. With a bar fridge under this, floating shelves above on the wall for bottles /glasses and DVD player etc, much easier to use the DVD when it's not in a cupboard love the room.

Is the door solid core? If not, a solid door would help somewhat, but would have to check the track can withstand extra weight. We have a couple of very heavy solid hardwood doors in steel frames which run on steel tracks. The bignheavy doors do dampen noise but certainly doesn't eliminate it entirely. Heavy drapery, rugs, soft furnishings, tapestries and large textile wall hangings will help to absorb sound from within the room, but still won't entirely eliminate it. If you don't already have carpet runners or rugs in your kitchen, adding some will also will help. Same goes for any other rooms which adjoin the music room/library. I knew a couple who soundproofed their small music room when they built their house. Their son played drums. As I recall, they used a special acoustic plasterboard for the walls, and the floor was carpeted. I think it helped considerably. there are also acoustic panels/tiles that can be installed on the ceiling, but this may be more trouble than it's worth. I'm not sure but the installation might be something like a suspended ceiling.

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