Sleep disturbances are known to be a prevalent problem in hospitalized, surgical patients, which is of importance since sleep disturbances can lead to a range of negative health outcomes. Music interventions have shown potential in improving sleep quality. Unfortunately, the studies on the effect of music on sleep in surgical patient populations are still scarce and of low quality. Therefore, the aim of this study is to study the effect of music on sleep quality in oncological, gastro-intestinal surgical patients in the form of a randomized controlled trial. Participants will be divided in 2 groups, a music group and a control group, where the music group will receive music interventions perioperatively. The researchers will compare both groups to see if there is a difference in sleep quality.

Inclusion Criteria:

• Patients aged 18 years or older
• Patients undergoing major elective abdominal surgery for malignant disease, including, but not limited to: Esophageal, gastric, colorectal, hepatic, pancreatic, gynecological and urological surgical procedures.
• Sufficient knowledge of the Dutch language.
• Communicable and able to assess the questionnaires
• Written informed consent acquired from the patient.

Exclusion Criteria:

• Patients with severe hearing impairment (defined as no or barely verbal communication possible).
• The patient is expected to be transferred to another hospital postoperatively.
• Participation in another study that may possibly intervene with the outcome measures. (e.g. in trial use of sleep medication, interventions regarding sleep quality or quantity or similar procedures)
• Assessment of primary outcome is not possible.
• Inability or unwillingness to receive the music intervention.
• Inability to wear the actigraphy device, or inability to perform actigraphy measurement due to paralysis.