This will be of interest to this discussion/report: https://aooke-anime.com/news/2327247.html On NHK's side of things, they announce it in this news item and the first episode (of the 5-minute program) is actually viewable outside of Japan here on their official broadcast listing.

It's just a matter of if these are specials or need to be added as a separate entry as the contribution bible isn't very clear on this (it's not like an extra story, and not all the episodes are showing on NHK's broadcast page of the anime).

I've watched all the extras directly on NHK-E, so I have been able to update those "Specials" that were already listed with some more info.

The 5-minute episodes (5分で楽しいクラシック "5 Minutes of Classical Music Fun") are basically a chibi Aono and chibi Akine in front of a blackboard discussing/answering various questions about classical music. There is a fair amount of live-action footage and there are interviews of some musicians from the NHK Symphony Orchestra in episodes 3 and 4 (which I've added as guest stars).

The 25-minute broadcast on March 16 contains some short previews of the anime, behind-the-scenes stuff, and interviews with the violinist who plays Aono's parts in the anime. Whoever added the 5-minute specials didn't add this, so unless the mods say it should be there, I haven't added it in either.

There's a good chance most of these extras will be on the BD/DVD releases later on (just a guess, it might not be).