Benny and Bjorn were good musicians, but as far as I can tell neither was classically trained. Wikipedia suggests that Benny taught himself how to play piano and indicated that Bjorn studied law in school, not music.
You are right to point out Agnetha and Frida's singing quality, but fail to recognize the vast difference in singing quality between Elvis and Bieber. I certainly hope the omission isn't suggesting that they were comparable.
I get your point that Elvis was a performer, but the man could flat out fucking sing. Elvis was a musician, his voice was his instrument. The same cannot be said of Justin Bieber.
You are right to point out Agnetha and Frida's singing quality, but fail to recognize the vast difference in singing quality between Elvis and Bieber. I certainly hope the omission isn't suggesting that they were comparable.
I get your point that Elvis was a performer, but the man could flat out fucking sing. Elvis was a musician, his voice was his instrument. The same cannot be said of Justin Bieber.