There’s something about seeing a person who’s fully alive.

Something about seeing a human being hitting on all cylinders, fully engaged in what he or she is doing.

But to see it twice within the span of 18 hours?

To see it in people separated by 46 years?

It’s enough to make you want to write about it.

We’ll start with the 47 year old.

He was dressed formally, as befits the performer at a recital.

But his manner was anything but starchy; it was inviting.

And he was inviting all of us in the audience to enjoy what to us was this new, unusual music.

It was music played on a piano with screws, bolts, nuts and rubber stoppers shoved in between the strings; music written in a way that used those screws, bolts, nuts, pink erasers and stoppers to create a different kind of sound, a variety of sounds.

These days, all the adjustments would be done by way of programming, and nobody would think anything of it.

But the music was written — imagined seems a better word — from 1946-48.

Deprived of software, composer John Cage instead used hardware, the kind found in a hardware store. That’s old school programming. The terminology was just different. What we’d call a programmed piano, he called a prepared piano.

All this, of course, was fascinating, as if Al, Tim Allen’s sidekick from the old show “Tool Time” had taken a wrong turn and walked into the studio in which “Great Performances” was being shot.

Following the music, which was projected on a screen, was just as interesting.

The score showed more changes in time signature than your average drag queen show. And all were needed for Cage to put what he heard in his head on paper so performers would have a kind of map to the sounds he intended.

That’s what written music always is, of course.

But usually, it’s a map to terrain people are generally familiar with, in which which the sound scape is familiar.

But in this case, it is not. And that makes bringing it off the page a greater challenge than adding water to frozen orange juice concentrate.

Sure the notes provides a guide. But to imagine the phrasing, translate that into the right touch, to turn notes into music, that, of course, is always the trick, make that the art.

And Chris Durrenberger was doing it on a bizarre scale in which screws, erasers and bolts had turned do-re-mi-fa-so-la-ti-do in to d0-ræ-mi-fâ-sØ-la-+i with the octave ending in Homer Simpson blurting out “D’oh!”

It was the process of focusing on pulling this off that Durrenberger seemed to be hitting on all cylinders. In the process of turning those marks we saw on the page into phrases, into music, he was coming fully alive.

The striving itself is part of it, like a bicycle whose mechanical headlight brightens and dims, depending on how fast it’s pedaled. But that leaves out something else: The thing that motivates you to get on the bike in the first place.

I have no interest in hastening Durrenberger’s death, of course. And I mention it here only because it makes me think of what’s so often missing from obituaries: the expression of how fully alive this person was. For surely, among all the mention of life accomplishments, the ability to be fully alive is among the greatest achievements.

And that brings me to the second person I saw fully alive: my grandson.

He’s not quite three months old. He’s spent most of his time on earth thus far in what I think of as the eat-and-excrete phase.

But when I saw him on his back beneath a mobile the day before the recital, something was different. With the soft music playing and the bright figures shaped like fishes rotating overhead, he wasn’t just an onlooker.

His arms and legs were churning. His eyes, lit up, were riveted on the moving objects. And though he’s not close to the age at which children form words, he was making noise like Dick Vitale at the Final Four, BABYYYY!

It’s unlikely the music of John Cage will light him up like that 46 years from now. But whatever can light him up like that?

I hope he finds it, as Durrenberger has.

Because there’s more to life than building a resume for your obituary.

There’s actually the feeling of being alive.