Does anyone know where I can get hold of the string orchestra version
,including the double bass, of Souvenir de Florence? I've tried Kalmus
(they sent one movt, no bass!) and all UK libraries.
Only the string sextet version was by Tchaikovsky, so you might be
looking for a more recent arrangement by someone else that's still in
copyright, which might explain some of the difficulties you've had in
tracking it down.
There is a new recording (Grammy nominee 2013) of this work, recorded
by Trondheimsolistene, re-arranged for standard string orchestra
(including double bass)
The arrangements are made by members of the ensemble; Contact Rolf Hoff
Apparently the bass parts were added by a Lucas Drew; finally located a
set of parts!