What is exactly the difference between f (forte) and fz (forzato) ? I thought for long time that fz is similar to sf (sforzando), i.e. that it's a punctual dynamic that works only at the moment where it's written, but just after the fz we use the same nuance (for example, if we are in p, then we want an accent at some point, and thus write fz, but just after the accent, we go back to p). However, I'm actually playing a piece where we are indeed in p, at some point the composer wrote fz, but in several interpretation I know, pianists stay in f. So, maybe sf and fz are quite different, and I was wondering if maybe fz could be sf +f. Could someone gives more details ?
Note that sf is often defined as subito forte rather than sforzando.
subito forte / sf / suddenly loud
sforzando / sfz / with a sudden accent
C. Humphries and R. Goldsby The Piano Handbook (2002)
sf / subito forte / suddenly loud
sfz / sforzando / suddenly loud
Matti Carter; Pianist's Handbook (2018)
It begs the question if a single note (or passage) marked sf (suddenly loud) after a piano passage means something different than an ordinary f after a piano passage if an accent isn't involved (i.e., sfz). Nonetheless, if I'm not mistaken, Schumann sometimes uses sf and sfz in the same piece.
From The Oxford Companion to Music (ed. Alison Latham, 2003):
forte (It.). 'Strong', i.e., loud; it is abbreviated f.
forza (It.). 'Force', 'strength'; forzando, forzato, 'forcing', 'forced', i.e., strongly accented.
sforzando, sforzato (It.). 'Forcing', 'forced', i.e., accented. In the 19th century it was used to mark an accent within the prevailing dynamic, but it has now acquired the connotation of sudden loudness; it is abbreviated sf or sfz.