quote:

Despite these limitations, the present study has made two important contributions. First, we now know that the expected phonesthetic effects are very strongly affected by real or even imagined familiarity, which means that large numbers of diverse languages must be tested. An interesting alternative is to use artificial languages, such as versions of Elvish or meaningless synthetic speech. Second, by setting an upper boundary on population-level esthetic preferences, we have emphasized the fundamental phonetic and esthetic unity of world languages.

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First, this is speech only, not singing/opera. So, any musical effect may factor into the "beauty" but is not a parameter, nor is it measured independently. In my opinion, the musicality of languages is fascinating. For example, the Met staged Florencia en el Amazonas in Spanish, (uncommon for opera) and it was pretty magical.

Second. Klingon was not mentioned as a possible alternative. :-)

Tl;dr No, but they found “a strong preference for languages perceived as familiar, even when they were misidentified, a variety of cultural-geographical biases, and a preference for breathy female voices.”