My test for English speakers who tell me they are tone deaf is to offer the most tonal two phrases I know in English - listen to the short audio below.
And 100% of them understand that the first one means 'yes' and the second means 'no.' The phonetic sounds are nearly identical. The key difference is in the tones. I first became aware of these tonal words in English when some of my high school students in Thailand came up to me after class and asked, "Ajaan Steve, What do mmm hmmm and mmmm mmmm mean?" I'd been using them in class unconsciously.
In Thai and Chinese the tones are part of each individual word - each syllable actually - but in English our tones are embedded in the sentences. We tend to have a rising intonation for questions, for example. Just say "no'
1. As though this is the third time your four year old asks if he can have an ice cream.
2. As though your girl friend has just turned down your marriage proposal, and you are checking in shock if she really said, "no."
Totally different tones.
This all came to mind today as I read a short piece about La Scala setting up a chorus for the tone deaf. I smiled when I got to this sentence:
"Maestro Maria Teresa Tramontin has directed the choir for the tone deaf since its formation, in 2010, at the suggestion of Luigi Corbani, who was until recently the director general of the Orchestra Sinfonica di Milano Giuseppe Verdi, known as La Verdi. "He believed that tone-deaf people didn't exist," Tramontin said." (emphasis added)
"In many cases, tone-deaf people have to be unblocked from a psychological point of view," Tramontin said. . .
Note: There may be some people who cannot distinguish tones, I guess. But then these people would have serious problems listening and understanding, let alone speaking, in countries that use tonal languages, as well most other languages, like English, where tones are connected to sentences rather than individual syllables. They wouldn't be able to say in perfect English, "I'm tone deaf, so I can't sing."