4 by RFBR (09-02-01355). The mode intensity for the “main” ˜ e ‖ a electromagnon (Δ ε$_{a}$ ≃ 2 [11]) is about 40 times stronger than electric contribution along the c -axis (Δ ε$_{c}$ ≃ 0 . 05) observed in the present experiment. The large electromagnon ab- sorption along the a -axis was one of the challenging ques- tions in explaining its origin. The relatively weak static electric polarization doesn’t fit well with the large dielec- tric absorption of electromagnon if both are caused by Dzyaloshinskii-Moriya interaction [26]. On the contrary, the Heisenberg exchange mechanism [18, 26, 27] seems to explain well the intensities of at least the high-frequency electromagnons above 50 cm − $^{1}$. In this model the edge- zone magnon couples to alternating orthorhombic distor- tions at oxygen sites via symmetric Heisenberg exchange interaction. This leads to the coupling of the zone edge magnon to homogeneous electric fields along the a -axis. As the symmetric interaction is much stronger than the relativistic DM coupling, the hybridized electromagnon has enough strength to explain the experimental inten- sities for ˜ e ‖ a . Much weaker [26] DM component can- not be seen in this experimental geometry because of the dominance of the intensity induced by the Heisenberg ex- change coupling. On the contrary, rotating the magnetic cycloid towards the ab -plane, both contributions can be well separated experimentally. The Heisenberg exchange part remain oriented along the a -axis, as confirmed by different experimental groups [15, 19, 26, 32]. The weak DM electromagnon rotates with the cycloid and can be clearly observed in the present experiment as electric con- tribution along the c -axis. One remaining question is: why we observe only one mode in the high-field phase? The probable reason is that one of two modes is too weak and is not seen in the spectra. This argument is supported by recent in- elastic neutron scattering experiments [31]. In these ex- periments the modes of the ab -plane spin cycloid have been investigated. Although this ab -plane orientation has been achieved using external magnetic field along the a -axis, the comparison to the present results is still very instructive. It has been observed that the excita- tions of the ab -cycloid are dominated by a strong mode at 2.25 meV [31]. This frequency corresponds well to the excitation at 21 cm − $^{1}$, seen in Figs. 2,3. In conclusion, we performed detailed polarization anal- ysis of the electric and magnetic excitations in TbMnO 3 in the high-field phase where spin cycloid rotates from bc - to ab -plane. The observed excitation at 21 cm − 1 could not be described by purely magnetic contribution as was suggested previously. We argue that this excita- tion is the missing electro-active eigenmode of the spin cycloid. 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