  The Witten deformation associated to a Morse function on a closed Riemannian
manifold, via Rellich-Kato theorem, relates analytically the spectral package
of the Riemannian manifold (eigenvalues and eigenforms) to the Morse complex
defined by the pair (Morse function, Riemannian metric) coupled with the
"multivariable harmonic oscillators" associated to the critical points of the
Morse function. We survey this relation and discuss some implications,
including the finite subset of the spectral package referred to as the
"virtually small spectral package" .
