In listening to a vinly LP last night of piano music I noticed that the notes aound middle C were slightly distorted.

I haven't come to a conclusion yet but I have heard piano will reveal acoustic and other problems in a system.

I am assuming that it may be caused by one or more of the follwoing:

1) The recording itself
2) The cartridge (Grado Gold)
3) The speakers (ML ESL's)
4) Room acoustics..

Any thing I may have missed and any thoughts on this?