Lomb-Scargle periodograms of the reduced light curve of V456 Cyg. Top: periodogram of the full reduced light curve of V456 Cyg, with the harmonics of the orbital frequency ν_orb indicated by full light-blue lines. Middle: periodogram of the full pulsation light curve. The frequencies that were detected from this light curve (ν_a to ν_n in Table 2) are marked in red. Full and dashed lines mark the independent frequencies and combination frequencies, respectively. Bottom: periodogram of the out-of-eclipse part of the pulsation light curve. The frequencies that were detected from this light curve (ν₁ to ν₁₁ in Table 2) are marked in red. Full and dashed lines mark the independent frequencies and combination frequencies, respectively. The dash-dotted line is the only combination frequency that does not include the orbital frequency ν_orb.