I take this from another post I made here rather than linking to it .
Mould and Mildew
Your saviour here is Juniperus virginiana, a North American juniper tree commonly and erroneously known as red cedar.
https://www.wood-database.com/aromatic-red-cedar/
Its wood has both fungicidal and insecticidal properties. It was used to line cedar chests, which many/most women in North America had in the days before central heating. Valuable clothing (woolens, silks, linens, leather goods, and furs), valuable books, and such were stored in them to protect them from insects and fungi.
The wood’s jointer and planer shavings from lumber mills used to be sold in pet stores for use in the cages of pet rodents as bedding – being very aromatic, it kept down odours . It is no longer used for this purpose because it generally poisoned the little rodents when they chewed on it – it is fairly toxic. It is now used on the floors of kennels and horse stalls where it keeps down both odours and fleas and ticks. But it can cause respiratory problems here. It is available in large bags from many horse tack shops. It is not expensive.
I have used it to treat vintage musical instruments - guitars, mandolins, and lutes and their cases - that have had mildew infestations. I have used it on vintage guitar amplifiers. I have used it on LP records and books. I have used it on 78s and their sleeves. There is no reason it could not be used on gramophone cabinets.
I make a tea. I fill a bucket with the juniper shavings, pack it down, and then pour boiling water into it. I allow it to cool and then filter it through multiple layers of cheese cloth. I use this as a wash for anything that can safely be washed – washing with a cloth soaked in the tea – for some things a damp cloth will be better than a wet cloth. Test first that the tea does not stain what you are working on. I do not rinse. I allow it to dry.
Then I pack everything (inside and out) with the dry shavings inside some airtight container, a large plastic garbage bag, a sealed box or crate - or whatever. Mechanical or electrical components of things I put in old pillow cases or sheets first. Instruments with F-holes get the F-holes blocked with cheese cloth – too hard to get the shavings and dust out. Then I leave it all sealed up for a month or two. The mould/mildew problem is generally solved.
For musical instruments, I generally place a laundry delicates bag full of shavings inside the case after treatment and refresh the shavings every few years.
For records, Lps, 45s, 78s, and sleeves, I have never had to resort to anything more than wiping with the tea dampened cloth – I have never washed them in the tea or with a wet cloth – before packing them away in shavings. After treatment, I clean them with the vacuum record cleaner, wet or dry as seems appropriate – and then let them dry really well before putting them away.