Why not the piano as a reference for bass

To my hearing,the lowest bass of the piano lacks the texture of a stringed bass..It strikes me as the kind of one note,thump thump bass you hear coming from a ricers trunk..
 I will however note that when it comes to physical weight & body,the piano is my benchmark..

@freediver what piano are you listening to that sounds like that?

Personally, I think it is because piano live is amazing but it is difficult to reproduce well, so most systems would fall short.  I have learned that over the years about horns.  I tend to agree with you though.  A good sample of test songs should include horns and piano to test a system’s ability to enjoyably reproduce those instruments.  I don’t listen much to piano, just not my thing, but have really started to enjoy horns - feels odd to even type that because when I first started my system made horn sound terrible.  

Piano goes low but wave length impact too short 

A pipe organ much better there 

Depending on music type