The 'three-ion' scheme (Kazakov et al 2015 Nucl. Fusion55 032001) is a new, high-potential ion cyclotron resonance heating scheme that has recently been proposed and experimentally tested. In this paper a simple cold plasma analytical model is introduced, which shows the beneficial effect of the changes of wave polarisation brought about by a tiny third minority when added to 2 majority ion species. This causes a second ion–ion hybrid layer to appear and allows to maximise the absorption of wave power on the minority ions. We also show by analytical modelling the effect of the wave interference on double-pass wave absorption in plasmas with two ion–ion hybrid layers.