Correlations between frequency bins for spectra generated with 10⁴ realisations, p_BH = 1 and differing initial mean eccentricities at orbital frequency ƒ_b = 2 nHz. The correlations get stronger as eccentricity increases, with the strongest correlations found for frequency ratios 2/3 (along the blue dashed line) and most of the correlated bins are expected to lie between the ratios 3/4 and 1/2 (shaded blue area).