  We study absolute zeta functions from the view point of a canonical
normalization. We introduce the absolute Hurwitz zeta function for the
normalization. In particular, we show that the theory of multiple gamma and
sine functions gives good normalizations in cases related to the Kurokawa
tensor product. In these cases, the functional equation of the absolute zeta
function turns out to be equivalent to the simplicity of the associated
non-classical multiple sine function of negative degree.
