Ultrasound scan is an image instrument that allows the assessment of diaphragmatic function and it does not have any side effects for patients. We have not found any literature about the use of M-mode ultrasonography to assess the diaphragmatic movement while singing. For this reason, in this paper we intend to assess this movement in two singers (soprano and contralto) after singing a high note and a low one. The diaphragmatic rise, measured as an angle of inclination, was smaller in the high notes than in the low ones in both singers an in all measurements taken. We consider that the study of diaphragmatic movement by using M-mode ultrasonography can be a study method of the behavior of this muscle while singing. This method, in the future, could be applied to the study of obstructive respiratory pathologies.