Temporal variation of the amplitude of additional frequencies in CoRoT Blazhko RR Lyrae stars. The CoRoT photometric light curves were split into eight chunks, the dominant pulsational frequency, its harmonics and the modulation side peaks were prewhitened. The Fourier spectrum in the vicinity of the additional frequencies (denoted by small vertical lines) are shown in the upper parts of the subfigures. Upper left: temporal variation of the half-integer frequency at 3 / 2f₀ = 4.1916 d^-1 and the independent frequency f′ = 4.03265 d^-1 in the Blazhko RR Lyrae 962. Upper right: the same for the CoRoT Blazhko RR Lyrae star 793. The frequencies are 3 / 2f₀ = 3.159 d^-1 and f₁ = 3.63088 d^-1. Lower left: the variation of f′ = 2.389287 d^-1 additional frequency in the blended CoRoT Blazhko RR Lyrae star 544. Lower right: the same for the Blazhko star 363, where f′ = 2.98400 d^-1.