Caetano, who always has a way with words, reminds us why it’s a good idea to practice the voiceless Brazilian R sounds:
“The fricative consonant allows the R’s, unlike the P’s, for instance, to be prolonged indefinitely. But whether in its properly fricative version, with the friction occurring between the tongue and the teeth (as in Italian), or in its guttural version, with either a strong aspiration (as in French) or one not so strong (as in Brazilian Portuguese north of Rio, unlike that of south of São Paulo, where the Brazilian R resembles the Italian), this prolongation is the prolongation of a sound into which the voice does not enter.
When the voice does intervene among the distinctive duration of the R, the effect is ridiculous to us Brazilians. There is a joke in which the narrator imitates a choir in one of those Paulista inland towns where the voiced R is dominant: when the conductor signals the end of the last bar of a song, ending in the word “amor,” the narrator dwells on the note, holding on to the horrible rolling sound of the liquid and vibrant R, rather than the vowel O. Frank Sinatra unwittingly recreates this comical effect in a song ending with the word “amore” or “before”.
But this is the very nature of the English language. We are inclined to find the Scottish R’s somewhat inadequate, while we admire the refined British who pronounce the intervocalic or nearly aspirated final R’s so dryly — as opposed to the coarser Americans who relish chewing on long, cavernous, supersalivated R’s, whatever the letter’s position in the word.”
– from Caetano’s marvelous autobiography Tropical Truth (which I recommend for anyone interested in Tropicália and the Brazilian counterculture)