Are the two peaks of the Cathedral QPO real harmonics?

We present a study of the two main peaks of the so-called cathedral QPO in XTE J1859+226. While looking at the temporal evolution of the two features we show that they do not manifest the same amplitude of variations of their power, and do not seem to follow the flux variations in the same way. We then present their RMS-spectra and show that they do not have the same shape, slope and cut-off energy. We discuss these different facts and try to answer the question regarding the genuineness of their harmonic relationship.