Researchers here may be interested in the concert database of the Hungarian Institute of Musicology (http://db.zti.hu/koncert/koncert_Kereses.asp). It appears to be in Hungarian only, though.
Köszönöm!
Ne említsd!
You guys!!
Seriously, though, it's a shame the database is only in Hungarian.
This (https://db-zti-hu.translate.goog/koncert/koncert_Kereses.asp?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=nl) may help.