Nicola[s] to the rescue

We have the answer to the musical curiosity, published a few days ago. Did you work it out?
[Photo of Nicholas, Nicola and Nicola]
Nicholas Newell, violin teacher says that when you first look at the music, it appears to be a B flat to be played by a treble clef instrument, such as the violin.

But Nicola Ball, pointed out that if you rotate the music anticlockwise 90 degrees, it looks like an A for the cello, written in the tenor clef [which cellos, trombones and bassoons sometimes use].

Then Nicola Jones pointed out that if you rotate the music once more, it now looks like a C for the viola, using the special viola clef. And Nicholas Newell, not to be outdone, pointed out that you could rotate the music one more time and have a natural B, as the music on that turn now has no B flat key signature.

So, reading the music around the 4 sides you get B flat A C B, which still doesn't sound like a composer's name ... unless you know that Germans call B flat B and B H. So now it makes some sense: B A C H