N.Y. U.C.C. 3-119

Section 3--119. Other Writings Affecting Instrument.\n (1) As between the obligor and his immediate obligee or any transferee\nthe terms of an instrument may be modified or affected by any other\nwritten agreement executed as a part of the same transaction, except\nthat a holder in due course is not affected by any limitation of his\nrights arising out of the separate written agreement if he had no notice\nof the limitation when he took the instrument.\n (2) A separate agreement does not affect the negotiability of an\ninstrument.\n