To me, these sorts of statements are just cultural stereotypes--languages don't have sound, people do. A French truck driver cursing out somebody who just cut him off is not going to sound more melodious than a Cantonese speaker reading poetry. But that's just me. Some Cantonese speakers buy into this Cantonese=cacophony idea, too:
"You might be saying, 'I love you' to your girlfriend in Cantonese, but it will still sound like you're fighting," said Howard Lee, a talk show host on Cantonese language KMRB-AM (1430). "It's just our tone. We always sound like we're in a shouting match. Mandarin is so mellow. Cantonese is strong and edgy."
I have heard this from speakers of Cantonese and Taiwanese. Perhaps what it is is that Chinese bilinguals ("bidialecticals"?) often use Mandarin for school and "official" business but their own dialect for more earthy matters. I can say from experience that most Taiwanese will switch from Mandarin to Taiwanese when they want to curse you out, and most of the few Taiwanese phrases I know are "edgy" expressions for that very reason.
The article also strangely conflates written Chinese and spoken Mandarin:
To stress a point or to twist a sentence into a question, Cantonese speakers need only add a dramatic ahhhhhhh or laaaaaaa at the end.Writing with fewer strokes makes the language more melodic?
Something simple like, "Let's go" becomes "C'mon, lets get a move on!" when it's capped with laaaaa.
By comparison, with Mandarin from China, what you see is what you get. The written form has been simplified by the Chinese government so that characters require fewer strokes. It is considered calmer and more melodic.
I would like to know why Mandarin is becoming more prevalent in the States. The article only says this:
But over the last three decades, waves of Mandarin-speaking mainland Chinese and Taiwanese immigrants have diluted the influence of both the Cantonese language and the pioneering Cantonese families who ran Chinatowns for years.The author says waves have been coming for three decades, but I think there's been a noticeable increase in Mandarin just over the last few years.
The surging Chinese economy today has challenged Cantonese further. Because Mandarin is China's official language, entrepreneurs [...] have been forced to adapt, often learning the hard way that business can't be done with Cantonese alone.