I'm not sure I get it, but there is no differentiation between a sequenced "sound" and the sound you play on the keyboard, if you are in the same layer. They're both the same sound, coming from the same source, and I can't think of anytime I've ever heard of any synth being any different in that regard. You could set up a split patch though, and have one layer for sequence and one for playing, that way you could accomplish what I think you're trying to do.
Also, be aware that if you're using only one layer for sequence AND playing, the sequence may steal notes that you hold...