Here is what HECTOR BERLIOZ (one of the most famous/influential French composers in history)
had to say about the Itallian Virtuoso M.A. Zani de Ferranti:
" Permit us to still speak to you with all sorts of praises,
and even with true astonishment at seeing a true master of his art,
lord of a spot in the musical domain. We have just heard Zani de
Ferranti, the last but the first of guitarists. Truly, it is impossible
to imagine the effects which he produces on this instrument, so
limited and so difficult. To Paganini's mechanism, Zani de Ferranti
joins sensibility and an art to sing, which, so far as we know, was
not possessed heretofore. Under his fingers the guitar dreams and
cries. It would seem that, nearing its end, it implored life. The
poor orphan of the lute and mandolin seems to say : ' Listen, how I
sing the beautiful melodies of Oberon — the king of genius ; how I
know the accent and deceit of timid love ; how my voice can unite
itself to the voice of mysterious tenderness ; the lute is dead, do not
let me in turn die also.' One could pass nights in listening to Zani
de Ferranti, he rocks you, he magnetises you, and one experiences
a kind of painful shock when the last chord of his poor protege
strains itself, giving vent to its grief — a mosaic silence succeeds.
We should also add that he writes excellent music for the guitar,
and that the charm of his compositions contributes a good share to
the prestige which it exerts upon its hearers."
I think he knew a thing or two of the guitar...but am curious to know like you brian, exactly how skilled he was.
Philip Bone on Berlioz: Berlioz was a guitarist of ample quality as composed some of his first compositions for the guitar before turning to the orchestrated stage and mastering the orchestra timbers and tones as well as reinventing the orchestra and its positioning and giving the orchestra a new "modifyed" purpose.
In his book on orchestration Berlioz says "One can not compose for the guitar well unless one is a guitarist." Berlioz also use to go to Felix Mendelsohns house and sing tunes by Moore while playing the guitar as acompanyment.
Basically, Berlioz was a guitarist for he knew the difficulties and technicallities with respect of the instrument as he was impressed by Ferranti, the Paganini of the guitar back in the mid 1800's.