In an experiment, 54 participants were instructed to play Twinkle, twinkle, little star using the Smule ocarina app on the iPhone, which involved blowing into the microphone of the iPhone and placing fingers on the screen to produce different notes.
One week after receiving instruction, the participants were randomly assigned to either an acute-stress induction procedure or a no-stress control group. The acute-stress group exhibited elevations in levels of cortisol as well as negative mood and arousal (as measured by two self-report measures of mood and arousal), compared to the no-stress group.
Participants in both groups were subsequently randomly assigned to one of three 10-minute-long activities: playing or listening to Twinkle, twinkle, little star on the iPhone ocarina or sitting in silence. Participants who had undergone the stress-inducing procedure and who played or listened to the ocarina during the stress-recovery period showed significant decreases in cortisol levels compared to those who sat in silence. However, as expected, participants in the no-stress group who played the iPhone ocarina showed significant increases in cortisol levels relative to participants who listened to it or sat in silence.
This according to “Effects of individual music playing and music listening on acute-stress recovery/Les effets du jeu et de l’écoute musicale sur le rétablissement d’un individu la suite d’un stress aigu” by Gabriela Ilie and Ramen Rehana (Canadian journal of music therapy/Revue canadienne de musicothérapie XIX/1  pp. 23–46).
Above and below, the iPhone ocarina in action.