  We study General Freudenthal Transformations (GFT) on black hole solutions in
Einstein-Maxwell-Scalar (super)gravity theories with global symmetry of type
$E_7$. GFT can be considered as a 2-parameter, $a, b\in {\mathbb R}$,
generalisation of Freudenthal duality: $x\mapsto x_F= a x+b\tilde{x}$, where
$x$ is the vector of the electromagnetic charges, an element of a Freudenthal
triple system (FTS), carried by a large black hole and $ \tilde{x}$ is its
Freudenthal dual. These transformations leave the Bekenstein-Hawking entropy
invariant up to a scalar factor given by $a^2\pm b^2$. For any $x$ there exists
a one parameter subset of GFT that leave the entropy invariant, $a^2\pm b^2=1$,
defining the subgroup of Freudenthal rotations. The Freudenthal plane defined
by span$_\mathbb{R}\{x, \tilde{x}\}$ is closed under GFT and is foliated by the
orbits of the Freudenthal rotations. Having introduced the basic definitions
and presented their properties in detail, we consider the relation of GFT to
the global sysmmetries or U-dualites in the context of supergravity. We
consider explicit examples in pure supergravity, axion-dilaton theories and
$N=2,D=4$ supergravities obtained from $D=5$ by dimensional reductions
associated to (non-degenerate) $ reduced$ FTS's descending from cubic Jordan
Algebras.
