I remember reading on the record jacket of a recording by Mstislav Rostropovich of the Bach Cello suites, a description that Rostropovich gave to each of the musical keys. I remember it being something like, "D major is optimistic and carefree, E-flat major is majestic and ceremonial, D minor is apprehensive but somehow optimistic", etc. However, hard as I tried with Google, I could not find any web page (book, article, interview, CD blurb etc) that has Rostropovich (or anyone else) on record making such a description. It could be that he was in fact describing each of the cello suites in these terms, as opposed to more generally the key that each suite happens to be written in.
Rather than this question be taken as a debate on the question itself, what I am really after is a source/reference: is there any citable intuition - expressed by someone somewhere at some point - about musical keys having intrinsic "feelings" to them?
Obviously, the common practice of transposition from one key to another suggests many people dont think there is any particular mood that one given key confers; that transposing is simply done for convenience, e.g. to fit the range of a certain voice/instrument.