composers asking for pedal during rests

[demented cow]

Sometimes composers ask for the pedal to be held down during rests, e.g. in the Chopin Barcarolle (Henle Urtext edition). I've never quite understood this, since when the pedal is down, it makes no difference when you release the notes with your hands. Any ideas on why they ask for this? Is it just because the pedal release is more reliable than hand release in getting all the strings to stop vibrating at exactly the same time, or is there some less mundane explanation?

[quantum]

It all comes down to creating different sounds.  When you intend to hold a note with fingers and also hold with pedal you produce a different kind of atack when you play the note, say as opposed to playing the note with the intention of releasing it while holding the pedal. 

This kind of technique became more wide spread with the impressionists, where the sonority of the piano was explorerd further.  If composers wanted even more specifically to say which notes were to be left alone to pedal, a notational convention was to put ties after notes that would end in open space and not connect to a second note.  Sometimes this is called laissant vibrer (let ring) - see Debussy Prelude Bk 1, No. 5 "Le collines d'Anacapri" for example of this.  Also another example is in Ginastera Sonata No.1 where the piano somewhat imitates a guitar at places. 

Is it just because the pedal release is more reliable than hand release in getting all the strings to stop vibrating at exactly the same time, or is there some less mundane explanation?

This is another method of using the pedal, although not much related to what I discussed above.  Using the pedal to control the release of notes is yet another tool to the pianist.  As pianists we usually only think of the attack of notes, because we have almost no way of actively influending the body of a note (Eg: as a violinist would insert vibrato).  But we can control how a note decays by slowing the rate at which the dampers contact the strings.  If we release a note with our fingers, normally we do this in a manner that lets the damper quickly mute the string, but if we use the pedal to control the dampers as they mute the strings we can change the manner in which the note decays (or ends).  This is also possible with fingers, but it is much easier to control with the pedal. 

[pianistimo]

thanks quantum!  i didn't know about the ties being tied to pedalling.