Background: Music intervention can reduce anxiety. This study analyzed the physiological changes from using music intervention after cardiothoracic surgery. Methods: Subjects were randomly assigned to the music group or the control group. The maximal inspiratory pressure/maximal expiratory pressure (MIP/MEP), pulse oximeter oxygen saturation (SpO2), visual analogue scale (VAS) for pain, and State-Trait Anxiety Inventory (STAI) were compared. Results: Compared to the control group (n = 9), the music group (n = 9) had higher MIP and MEP during the overall test (p < 0.05), with significant differences in the changes and time (p < 0.001). However, only MEP was significant in terms of the interaction between music intervention and time (p < 0.001). In terms of the groups, SpO2 and VAS were significant (p < 0.05). SBP, SpO2, and VAS over time showed significant differences between the two groups (p < 0.05). In terms of the interaction between music intervention and time, only SpO2 was significant (p < 0.05). The STAI-S scale decreased by −5.7 ± 5.8 in the music group vs. −0.47 ± 9.37 in control group and the STAI-T scale increased by 4.17 ± 12.31 in the music group vs. 1.9 ± 9.29 in the control group, but showed no significance. Conclusions: Music intervention with nature sounds has a positive physiological impact and can reduce postoperative pain and anxiety in cardiothoracic surgery patients.