Comparison of the variation of the first three harmonics (typically those with the largest amplitude) of the Fourier series as a function of energy. The sources are in order from top to bottom: Vela X-1 (type 2), GX 301 – 2 (type 2), Cen X-3 (type 1), 1E1145.1–6141 (type 1), LMC X-4 (type 0), and IGR J16393–4643 (type 0). The boundaries of the energy ranges are [0.5, 2, 3, 4.5, 6, 9, 12, 15, 18, 27.6, and 78] keV with the exception of IGR J16393–4643 whose energy ranges are [3, 6, 12, 15, 27.6, and 78] keV. Blue symbols represent XMM-Newton data and black symbols NuSTAR data.