  We have detected the (0,11c,0)J=3-2 and (0,0,0)J=8-7 transitions of HCN
towards the S star {chi} Cygni. The excitation requirements of these
transitions are too high to be satisfied in the outer envelope of the star, and
the emission must originate within {solar}20 stellar radii, ie. the molecule
must be forming close to the star. This conclusion is supported by a model for
AGB stars in which molecules including HCN form in a shocked wind close to the
stellar surface.
