I gotta be honest, I'm thinking it's fake news akin to "Kim Jong Un Haircut Law". I can't find any non-english sources about it. I can't find the article TASS reportedly posted about it either. I can't find Dadayev speaking about it anywhere but in these english articles.
It should be noted that I am completely shit at doing this kind of digging and I do not speak any slavic language nor do I read kyrilic, so me not finding things doesn't mean a lot
It seems to be legit actually, I found this article by gazeta.ru, which Wikipedia classifies as Russian state-controlled media claiming the same thing. In the article is this quote:
This was reported by the Grozny-Inform portal with reference to the Minister of Culture of Chechnya Musa Dadaev.
If someone here actually speaks Russian feel free to correct me though.
“Today, under the leadership of Musa Dadaev, an extended meeting was held with the leaders of creative state and municipal groups of the Chechen Republic, during which he announced the final decision, agreed with the Head of the Chechen Republic Ramzan Akhmatovich Kadyrov, that from now on all musical, vocal and choreographic works must correspond to a tempo of 80 to 116 beats per minute,” said the Ministry of Culture of the Chechen Republic.
I think this is going to apply to theaters, musicians, etc.
After the quote there's "huge work is ongoing on the question of Chechen musical, choreographical and other works matching Chechen mentality and musical rhytm", so it is probably the latter.