  A Fourier analysis of double-spin azimuthal asymmetries measured at HERMES in
semi-inclusive deep-inelastic scattering of longitudinally polarized leptons
off tranversely polarized protons is presented for pions and charged kaons. The
extracted amplitudes can be interpreted as convolutions of transverse
momentum-dependent distribution and fragmentation functions and provide
sensitivity to, e.g., the poorly known worm-gear quark distribution.
