The Wikipedia page for the Hare Krishna mantra provides some evidence that the mantra provides joy through the singing of certain vowels:
In a 2010 experimental study involving both devotees and non-devotees, singing vowels like "ah" and "eh" was found to be more joyful than singing vowels like "oh" and "uh", possibly due to a facial feedback effect.
They have a reference:
Böttger, D. (2010) To say "Krishna" is to smile - emotion psychology and the neurology of mantra singing. In "The Varieties of Ritual Experience" (ed. Jan Weinhold & Geoffrey Samuel (fr)) in the series "Ritual Dynamics and the Science of Ritual", Volume II: "Body, performance, agency and experience". Wiesbaden, Germany: Harrassowitz. Video Summary
I'm unconvinced by the summary of this study.
Does the singing of certain vowels lead to more joyfulness?