[LAU] Synths and sequencers again

Does anyone know of a good tutorial on how to make use of a synth? I know how to work it from a user manual perspective, but I have no idea what to do to get a reasonable sound out of it. What I really want isn't so much a full blown synth. Take any of the sequencers which play soundfonts. For any given instrument (piano, strings, etc), there are many many different versions (e.g. grand piano, bright piano, electric piano, etc, or even several different sounding grand pianos for example). What I'm looking for is something which will allow me to make small alterations to any given instrument. I'm particularly thinking of strings- take a "string ensemble" soundfont. Firstly, there must be all sorts of small variations you could do to make it sound a bit different. Secondly, these are incredibly difficult to control. Mainly because of the way they will sustain forever- it would be useful to have more sane handling of the pedal and ADSR (plus a bit more) manipulation. Any ideas if this is possible? I noticed the other day that attack and decay time are defined as standard midi controls. Does anyone know if things like fluidsynth pay any attention to these? Thanks Simon