Would anyone think this could apply to LIBOR?
2.9 New York Law of Mortgages
2.9.4 Underlying Obligation39
The general rule in New York is that a security interest or mortgage can only be valid where it is supported by an underlying and enforceable debt or obligation.40 The underlying obligation or debt are generally evidenced by a note or bond separate from the mortgage or security instrument, the note or obligation can also be contained in the mortgage instrument itself.41
An obligation or debt sufficient to support a mortgage must be capable of being reduced to a finite monetary amount.42 The amount and terms of the debt or underlying obligation must be identified with reasonable certainty in the mortgage or security instrument43 and only those amounts explicitly covered by the mortgage will be covered in the secured debt.44
If the underlying obligation is invalid or unenforceable, the mortgage will no longer be a valid security instrument or device.45 If the interest rate is illegal as usurious, the underlying debt may be declared invalid.46 Likewise, a gambling debt will be considered illegal and unenforceable.47
A mortgage can secure future debts or advances if they are obligatory on the mortgagee to lend the money indicated in the mortgage instrument.48 Where, however, the debt is optional, the lienor will only prevail to the extent that advances are actually made and intervening parties have not achieved superior equities or rights to the security interest.49
Where the mortgage debt has been paid, the security interest expires.50 Where the bond and mortgage are in possession of the mortgagor, this gives rise to a presumption that the debt has been paid and the mortgage has been discharged.51