Good Materials for Curtains

Has anyone made heavy curtains specifically to add absorbance to a room, and (of course) to block the reflections of glass? If so, what materials did you use. This is such a simple and common acoustical technique, yet I can find little written about what types of fabric (etc) are best. Thanks for your experienced suggestions.
Probably not talked about much due to the fact that most men don't get to choose - WAF rules. :-) But if I wanted to deaden the sound I would use lined wool. If I wanted to reduce the sound, as in making it diffused, about any other materiel would do so long as its not sheer.
I asked a similiar question back in Jan./03....this was Richard from Rives Audio reply

01-11-03: Rives
Hunter vertical blinds makes a Honey comb. It works quite well for some absoption and diffusion. For absorption heavy natural fiber of two different types, have a liner of heavey loose woven material like denium or wool and a lighter fabric on the outside. You need a gather of about 50% when the drapes are closed. This will work quite well. Short of replacing the inserts in the glass there is little you can do about the bass leakage.
Rives (Threads | Answers)
I put up some velvet curtains on the front and side walls and they seem to have eliminated enough of the early reflections to increase focus, depth and imaging quite noticeably.
Get the curtains that look best in your room and then get the AudioPrism vibration control dots to tune-in your windows. Velvet curtains??? Yeh, baby!!
If you live in a city, I would use curtains that shield against RFI, something with a metal braid woven inside them.
If I may, I know the curtains won't soundproof. but why the companies claim that they're making soundproof curtains see reviews on them at the first time. 

It might knock down a bit of the upper frequencies but the mids and low end will go right through it.
I would suggest buying the heaviest natural material offered in the width and length you require. In back of them on the same or on an additional rod have a slightly smaller pair of wool blankets with with slits cut into the top that will go on the rod as a backing panel. You can conceal any appropriate material behind the chosen curtains so that it is inconspicuous to everyone but you and your significant other. The heavier the materials the more bass absorption you will experience. As always your mileage may vary. It may take some tweaking. Isn’t audio FUN!🤡
I think a lot of it depends on whether you’re naked or not whilst listening to your HiFi.
These curtains are meant to block outside noise more than provide a sound treatment for a room. Probably will do both, however.
I've never needed to use ... but if I did, I would try the "Block out" curtains. They are for blocking out the light... and so they have a rubber backing. I think that would do wonders over just  fabric alone.
Vinyl is very good for sound absorption - I have used a vinyl roller blind behind the listening position and in front of a window with great success.

The blind only had to be extended about 18-24 inches for optimum  benefit/effect.

I have also tried a strip of vinyl 8 ft x 2ft in an open plan concrete condo again at ceiling height (12ft high) behind the listening position and at one side between the open plan kitchen and the listening area.

My new basement listening room has several dropped portions of ceiling to accommodate heating ducts, which seems to trap unwanted reflections at ceiling height. The room is also irregularly shaped, which also helps a lot

I have seen a couple of acoustic specialists which incorporate vinyl into their products

It would appear that the vinyl does not have to be very thick, which helps with the weight problem

Hope That helps - Steve