Some of the spounds that feature included vibrato work better when played in a more staccatto style. That way, when you DO hold a note, the vibrato kicks in and sounds realistic. In a ballad setting, you need a combination of "none and some" when vibrato is used. That's they way a horn player would apporach it. In some cases, it's better to control it manually with a wheel, slider or aftertouch ... whatever is available to you.