No, that was his cousin, Meno Mosso. You’re thinking of Pie Jesu*, who was the shortstop for the Dodgers back in ’74, before they traded him to the White Socks.
Actually, those are both musical terms, describing how a composition is to be played or sung. Composers generally include descriptive terms to indicate the “mood” and pace of a piece, beyond just the notes on the page. How many quarter notes (or half notes, or eighth notes) in a minute, the feel of the tempo – fast as in driving, fast as in lively, fast as in frenetic – and how connected the notes are supposed to be. Instrumental composers, since they don’t have a text to use to clue in their musicians, lean a lot on “andante” “largo,” “piu mosso” and their cousins. Often, a full symphony will be divided into movements titled after the tempo. “Andante,” then “Largo,” then “allegro,” and so on.
The slowest I’ve seen, and that rarely, is “lento.” This is slow, often mournful. “Piu lento” means a little more lento, but don’t drag. In choirs, we tend to push really, really slow tempi, often because we feel the need for air. Orchestras can go even slower, and do, but choirs need to breathe. Or at least, we think we do. Timing a “lento” is up to sixty beats per minute, or one beat a second, but usually slower. Often the eighth note will get one beat, slowing things even farther.
More common in the music I’ve done is “largo.” Largo is thoughtful, dignified, but not painfully slow. Largo reminds me of paddling slowly across a lake. These are your deep, swelling chords, rising and falling like great waves on the sea. Next comes “adagio”, stately and steady. The so-called “Albiani Adagio” is probably the most famous adagio. Often a movement in a symphony will be labeled adagio. There may be faster bits in the over-all adagio feeling, but the general “push” of the music is slow to moderate.
Andante is a steady walking pace, if you are not walking with me. (I walk allegro). It’s your basic not too fast, not too slow, we’ll get there tempo. Choirs like andante. Orchestras see andante as a lead-up to allegro or presto, or a respite from allegro and presto. String players appreciate andante and slower, while the woodwinds and brass sometimes express doubts. (Remember, orchestra brass and woodwinds don’t breathe. Choirs breathe. Strings and percussion can do whatever the heck they want, and the pianist has a beer on the music-rest so he’s not worried about anything!) When in doubt, andante.
Allegro and vivace are “trot” and “look lively and run fast.” Allegro can be used for choral tempi, but vivace is not all that common. Usually, the composer just changes the time signature, so that instead of a quarter note getting one beat, it is the half note. That means the music suddenly goes twice as fast. At least. Beethoven, I’m looking at you. (The second half of the “Credo” in the Missa Solemnis, the “Et vitam venturi saeculi” portion.)
A musician may also see French, German, and English terms as well, and their general sense is understood. I’ve not seen much French annotation aside from organ music, but I’m very familiar with the German (organ again, and other things) and English.
“Piu” means more of whatever it was. “Meno” means less of it. So a piu mosso direction calls for a bit more speed and a more sprightly style. Meno mosso is a call to rein it in, slow a little, connect the notes more so the tempo sounds slower.
Conductors are free to shift things around, and all these instructions are a range. Some choirs and orchestras or soloists can do certain things faster, or slower, and the conductor’s job is to work within the broad sense of pacing and speed to get the most feeling or precision, or both, out of the group. Unless the composer is standing there, correcting things. Then you listen to the composer.
*”Pie Jesu,” pronounced pee-ay yay-sue, is Latin and is also the title for a movement in the mass. Although I’ve heard a conductor order a choir to “sing it like the Lloyd-Weber ‘Pie Jesu’.” It worked, because we all knew what the composition sounded like.
For more than you ever wanted to know: https://theonlinemetronome.com/blogs/12/tempo-markings-defined