The intervention protocol is based on four main themes, which are addressed over the course of eight sessions:

• Self-care
• Self-recognition and expression of emotions
• Empathy
• Teamwork

Each theme is related to factors from the HUMAS (affection, self-efficacy, emotional understanding, dispositional optimism, and sociability) and/or ProQOL (compassion satisfaction, burnout, and compassion fatigue). A variety of techniques related to the four main methods of music therapy will be used in the sessions: receptive, re-creative, composition, and improvisation.

The HUMAS was developed by Pérez-Fuentes et al. and has been validated in Spanish among nursing professionals. It consists of 19 items evaluated on a 5-point Likert scale, with a total score ranging from 0 to 95, with higher scores indicating greater intra- and interpersonal skills that favor the humanization of the service provided. The items are divided into 5 factors: affection; self-efficacy: emotional understanding; disposition to optimism; sociability.

The ProQOL measure is one of the most widely used scales to determine quality of life in health professionals. It consists of 30 items rated retrospectively (over the past month) on a 5-point Likert scale. The scale measures the following factors: compassion satisfaction, burnout, and compassion fatigue. Each factor scores from 0 to 50, with higher scores indicating a greater satisfaction with an individual's work (compassion satisfaction) or higher scores indicating greater experience of fatigue, stress, or emotional exhaustion (compassion fatigue and burnout). The psychometric properties show satisfactory internal consistency and discriminant validity and it has been recently used in nursing teams in emergency units.