I have not tried Elroy ER211, ER242 uses a different anode, so the sound can well be different.
As for ER242, I don’t think there is any problem playing classical music. It is a very well made and good sounding 211. It is the best modern tube I have tried. I find myself listen to ER242 more than other tubes. If you are not looking for the vintage tube sound given by GE or RCA, Elroy is a good choice.