  In 2016 and 2017 COMPASS has collected a considerable amount of deep
inelastic scattering events with a 160 GeV/c muon beam and a liquid hydrogen
target. An analysis of 4 % of these data has allowed to extract preliminary
results on the amplitudes of three azimuthal modulations,
$A_{UU}^{\cos\phi_h}$, $A_{UU}^{\cos2\phi_h}$ and $A_{LU}^{\sin\phi_h}$. The
first two are particularly important since they carry information on the
intrinsic transverse momentum $\vec{k}_T$ of the quarks and on the correlations
between the quark spin and $\vec{k}_T$, expressed by the Boer-Mulders TMD PDFs.
They show strong kinematic dependence as a function of the Bjorken variable
$x$, of the fraction of virtual photon energy carried by the hadron $z$ and of
the component $P_{hT}$ of the hadron momentum orthogonal to the virtual photon
direction, thus confirming the results of previous measurements. Also, as was
recently shown by COMPASS, hadrons coming from decay of diffractively produced
vector mesons give significant contribution to the amplitudes in certain
kinematic regions, explaining in part the kinematic dependencies and helping
the interpretation of the measurements. The effect on the published COMPASS
$^6$LiD data is discussed.
