Layered sounds which are set up in a crossfade situation ALL start when you hit a key. All the crossfade function is doing is changing the mix balance between the two samples.
It looks to me like your problem is that, while both your looped sound and your \'single shot\' crescendo sound are layered, they both start streaming when you hit a key and by the time you change the balance so that your crescendo sound gets a look in - it\'s run out.
There\'s not much you can do about this in a standard Giga crossfade situation.
This is where GST3\'s midi rules will be a major boon, I think. It will probably be possible to set a rule so that the \'key on\' trigger for your crescendo sample could be, for example, the point at which the mod wheel moves away from its 0 position. That way your unlooped crescendo only starts to stream when you are about to \'expose\' it. It\'ll save on polyphony too [img]images/icons/smile.gif[/img]
In the meantime, maybe your better off to use two separate tracks and instruments - one for sustain and one for crescendo. Perform the main track, then copy the notes which will need the crescendo, and do a bit of note offsetting.