I keep thinking about this, so because today is Puccini's birthday, I have decided to post it. At least a month ago I attended a performance in the Crocker Art Museum. I won't name the singer, but her program included a group by Puccini, including "O mio babbino caro."
One programs "O mio babbino caro" to show off ones mastery of the Puccini style, specifically scooping and sliding. Angela Gheorghiu may be considered a master of this style, and performs it with at least 15 scoops and as many slides. Now try to imagine that someone would program this piece and not scoop or slide even so much as once. It was deeply shocking. I am still asking myself why.
Sliding. A properly executed vocal slide goes from an upper note with a glissando to a lower note during the duration of the upper note, and lands on the lower note just at the right time to sing the lower note with the new word. To emphasize the slide the lower note may be delayed by extending the glissando. The slide ends with an anticipation of the next note.
Scooping. A scoop approaches a note from below and begins at the time of the new note. It's like you start flat and rise gradually to the right note. A properly executed scoop must end in tune.