Wow I too have the same glass above my doors. Mine are all internal swing doors therefore I don't have your delema. I'm in the middle of renovations and mine are staying. My walls will be dark and modern with all the trim white with the original character and it looks great. With your wall, it's a lot to deal with therefore would suggest replacing the slider with a glass door with timber trim, keep your walls light modern and bright and paint your trim dark (any colour you favour) here is my example to give you an idea of what I'm talking about hopefully you can see the value here is a snippet of my renovation good luck....hope my idea gives you plenty of ideas

Andy Pat here is a current photo (mind the existing colours). Thanks everyone for your comments. Will be watching the block to see how they restore those homes. Think I will be keeping the original wall sheeting at this stage but as mentioned above running new services could be an issue (as there isn't a lot of power etc currently). Think a new plasterboard ceiling will be the extend of plasterboard upstairs (the existing is made up of a chipboard compound that is falling away in parts.

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.

Hi Kate, If you are looking to keep the mid century style I suggest you go with a flat solid core door like the pic below. Very popular at the time was to stain and varnish, keeping the grain visible, but you can also just go for a painted finish. Combined with a lever set like the one above for a modern take on Mid-Century classic style. Hope this helps, MKG