“Jumping” on high notes means to take them from below, but not in the sense that the singer is out if tune and he doesn’t quite reach it, arriving short, and adjusting it afterwards. And it’s not even a glissando, or a portamento, which can be really annoying. Rather, the singer “jumps” on the note, bouncing for a second on a lower note, like a gymnast bouncing off a springboard. It’s not a mortal sin, if you don’t do it too much; often it is actually a way of interpreting the music. But you should use it sparingly.
Examples. Let’s take a phrase in the famous aria Una furtiva lagrima, where the words are “quelle festose giovani”. On the three syllables of the word “fe-sto-se” the tenor must sing E-G-F, and often the tenors don’t fully reach the G on the syllable “sto”, but bounce off the E (i.e. they say “sto” for a second on the E),
The attack of the flower aria in Carmen, on a high F, is a typical point where tenors often “jump”, bouncing for a second on the D flat.
Now we continue pistol-whipping blind kids, and we listen to Alagna, who jumps a third up, and finally lands on the F.
Our Andrea Carè’s jump is not so bold as Alagna’s, and, I must say, much more graceful. Beautiful voice.
And now, let’s clean our ears with someone who never sang a high note other than perfectly. Observe how he never jumps. On the words “te revoir, ô Carmen” he actually does a glissando, in order to communicate passion. The following high note, on “Car tu n’avais eu qu’à paraître“, is the same note, and he takes it straight on, wonderful. Jussi, we miss you so much.