subroutine nmo1( conj, add, slow,    x, t0, dt, n,zz,  tt )
integer  it, iz, conj, add,                        n
real  xs, t , z,            slow(n), x, t0, dt, zz(n), tt(n)
call conjnull(   conj, add,                     zz,n,  tt,n)
do iz= 1, n {
	z = t0 + dt*(iz-1)
	xs = x * slow(iz)
	t = sqrt ( z * z + xs * xs)
	it = 1 + .5 + (t - t0) / dt		# Round to nearest neighbor.
	if ( it <= n  ) {	if( conj == 0 )
					tt(it) = tt(it) + zz(iz)
				else
					zz(iz) = zz(iz) + tt(it)
				}
	}
return; end