As symbols of love, diamonds display facets. Like life, they derive from carbon, trapped under extreme heat and pressure, but once stabilized — metastabilized, in fact — to equilibrium, they're among the toughest substances in the world. The name derives from the Greek adámas, with multiple meanings: unbreakable, proper and untamed. Diamonds rise to the surface through volcanic eruptions, conduct heat and discourage impurities. Under light, they cast spectacular spectra of the rainbow.

Yet with all those metaphors easy to hand, lyricists — male, notably — see diamonds not as pure love, but its substitute. In John Barry's "Diamonds are Forever," theme song from the 1971 James Bond film, Shirley Bassey sings: "Diamonds are forever, they are all I need to please me/They can stimulate and tease me/They won't leave in the night/I've no fear that they might/desert me."

Jule Styne and Leo Robin shaped that cut with the earlier "Diamonds are a Girl's Best Friend," from their 1949 musical "Gentlemen Prefer Blondes," probably best known as crooned by Marilyn Monroe in the 1953 film: "Men grow cold/As girls grow old/And we all lose our charms in the end./But square-cut or pear-shaped/These rocks don't loose their shape/Diamonds are a girl's best friend."

John Lennon and Paul McCartney's "Lucy in the Sky with Diamonds," also being performed in Monday night's collaboration between the Tuscaloosa Symphony Orchestra and the University of Alabama Opera Theatre, doesn't follow that cooling trend: Lennon was inspired by a drawing by his then nursery-school aged son Julian, making him one of the youngest, most successful muses in pop music history, considering that McCartney wrote "Hey Jude" originally as "Hey Jules."

Unless you count Rihanna's "Diamonds," or the implied engagement stone of Beyonce's "Single Ladies," those three are probably the best-known songs that fit the TSO-Opera Theatre Valentine's Day-themed collaboration, "Diamonds Are a Girl's Best Friend."

"We work together beautifully," said Paul Houghtaling, director of opera at UA, of his teaming with TSO Music Director Adam Flatt, who'll conduct the orchestra. Houghtaling and his voice students joined for a similar Valentine's concert in Flatt's first full season here.

"We did a show called 'Let's Fall in Love,' with a similar mix of musical theater, operetta, group arrangements," Houghtaling said. "It was a huge hit, fun for the orchestra, fun for the audience and the students. Finally the timing was perfect to do it again."

The theme idea arose over drinks with Jenny Mann, executive director of the TSO. For years, symphony benefactor Gene Poole and his Hudson-Poole Jewelers have donated a piece of diamond jewelry to the Valentine's concert as a prize, with the winner drawn randomly from among ticketholders; Poole's appraiser is a cousin of Houghtaling's.

So it's been in the planning over the past year, with arrangements of "Lucy in the Sky with Diamonds," "Diamonds are a Girl's Best Friend" and "Diamonds are Forever" commissioned last summer, created by California-based composer Joshua Feltman.

"They're jazz harmonies, super cool, and everyone is featured as a soloist," Houghtaling said. "We have two arrangements of ('Diamonds are a Girl's Best Friend'), first as women only, then as a group number at the conclusion, so we are driving the theme hard."

The evening also spotlights works by Italian composer Giacomo Puccini, with the orchestra featured on his "Capriccio Sinfonico," and Intermezzo from "Mason Lescaut." Opera Theatre soloists Garett Torbert and Christopher Withrow sing his "Nessun Dorma" from "Turandot," and Torbert and Lydia Beasley will take the solos on "O Sauve Faniculla" from "La Boehme."

Houghtaling will join Beasley and Marie Smithwick as soloists for Wolfgang Amadeus Mozart's "Soave sia il Vento" from "Cosi Fan Tutte," and Chance Anderson will sing "Where'er You Walk," from George Frideric Handel's "Semele."

Representing musical theater will be not only the Styne-Robin title song, but Jerome Kern's "Bill," from "Show Boat," with Beasley as soloist, and "I Feel Pretty," from Leonard Bernstein and Stephen Sondheim's "West Side Story." Like the opening number, "I Feel Pretty" highlights the women, with Alexandrea Nessi, Julia Schwendenmann, Emily Knowles, Kirkland Schuler, Isabella Powell and Miranda Shapiro featured.

"In a very timely way, this concert celebrates women," Houghtaling said, "which works out, given our current socio-political situation."

But the men aren't denied gems, singing the Beatles as a quintet, with Nicholas Reese, Scott Willis, Tyler Koch, Noah Rouse and Christopher Withrow as soloists on probably the second or third-oddest song from "Sgt. Pepper's Lonely Hearts Club Band." They're also included in the finale reprise of "Diamonds are a Girl's Best Friend," and elsewhere throughout the program.

Flatt and Houghtaling will share the podium.

"It'll be Adam and I talking...mostly me," Houghtaling said, laughing. "Adam's very soft-spoken, and I'm not; it'll be fun for us to banter on stage."

Some tickets remain, from $10 to $40, through the website at www.tsoonline.org, or by calling 752-5515. The pre-show Cheers 'n' Chat reception will be 6 p.m. Monday in UA's Moody Music Building Choral Opera Room. The concert will begin at 7 in the Moody Concert Hall.