What is the most challenging music to play on a stereo?

For me, busy rock music with piano.  Large bands with many instruments competing for space are challenging to record and mix and then reproduce.  If this can be resolved then I'm always impressed.  

I started to say 'Piano' because of the dynamic range and impact of a Grand Piano. Tough to set up a system that can do this, even if you've found a recording where the engineer had succeeded.  But on reflection it has to be classical orchestral music where you have a much more apparent dynamic range and integration with a symphony hall as well as appropriate sound from different points in the hall. Too much to expect anything that is really live like. With a piano you can come a bit closer I think. One of the killers in orchestral recordings is the practice of spot lighting strings for example. Often bright to the extreme on a recording but rarely so in a live event. But its all good anyway.

The Dan! yes, the question could use refining though.  If the recording is bad, any kind of music. A bad pressing or mastering what ever.  If the recording is noisy or compressed or has background noise that makes it hard to play, or listen to.  If the recording is a good one,(any type of music, even country or Hair Metal), the stereo has a better time delivering it.  A quip comes to mind, "Don't shoot the messenger".  

So even the "Dan" as in Steely, can be a test for a system, but at what volume?  In what room, and so on.  

But to the assumed meaning of the question, I say Piano is the hardest to process for a stereo at any volume or in any room played by even a master!  

I’ve read a phrase here that stated “help, my Steinway sounds like a banjo”. I always recollect to this phrase when listening to solo piano. Months ago I was invited to a friends home and they have a vintage Steinway Baby Grand (which was just tuned). I had him play a few things and also played with the piano myself (the little I can bang on the keys) and I noticed there is a little muffle when the the hammer hits the strings. The hammer has some sort of velvet on it and so the instant that hammer hits the string, the note is actually not as airy and sharp. For the Tube amp guys here I would explain it as more of a Mullard EL34 sound vs Gold Lion KT77. Hope that makes sense.

@pangeek --

Yes, all the hammers on a true acoustic piano are padded. Some brands more than others. As the piano is played and the hammers strike the strings, they eventually compress & harden up and produce a brighter tone. When things go a little too far, a piano tech might soften the hammers, giving them a bit of their previously rounded tone.

I never owned a Steinway (I just never had the lucre), but the ones I lovingly "tested" at the piano dealers varied immensely, from bright to mellow. I have to say, though, that they never sounded rinky-dink.