THe question of whether a signal is completely described by these aspects, or of there is a mysterious "X" aspect that will distinguish two signals that are identical in every way known to engineers is outside the domain of signal analysis, and could be termed philiosophical in nature. I suspect this "X" aspect is really the internal state of the listener, so, in a good modd a signal will sound one way to the subject, and if he/she were in a bad mood, the identical signal (identical from an engineering perspective) will be perceived quite differently by the same subject.
-akhilesh