In IDEAL-type sequences, spectral selective pulses are done with an excitation frequency fe dependent on the slice position, and the acquisition is applied with a reception frequency fr. For a proper spectral study, the phase observed during the different evolution times of each shot (TE) has to be dependent only on the CS. A phase coherent fe-fr switch is applied throughout the pulse sequence. However, depending on the frequency commutation position, phase errors are accumulated, disturbing the CS study. This presentation elucidates the impact of the commutation's position and how to correct to resulting phase errors.