  We demonstrate how to overcome serious problems in understanding and
classification of vibration spectra in semiconductor alloys, following from
traditional use of the virtual crystal approximation (VCA). We show that such
different systems as InGaAs (1-bond->1-mode behavior), InGaP (modified 2-mode)
and ZnTeSe (2-bond->1-mode) obey in fact the same phonon mode behavior - hence
probably a universal one - of a percolation-type (1-bond->2-mode). The change
of paradigm from the `VCA insight' (an averaged microscopic one) to the
`percolation insight' (a mesoscopic one) offers a promising link towards the
understanding of alloy disorder. The discussion is supported by ab initio
simulation of the phonon density of states at the zone-center of representative
supercells at intermediary composition (ZnTeSe) and at the impurity-dilute
limits (all systems). In particular, we propose a simple ab initio `protocol'
to estimate the basic input parameters of our semi-empirical `percolation'
model for the calculation of the 1-bond->2-mode vibration spectra of zincblende
alloys. With this, the model turns self-sufficient.
