'Why?" is a question every aspiring journalist is taught to ask - and answer.

Yet, in my current incarnation as an art critic, when I find myself confronting a work and asking "Why?" it is usually a sign of trouble. Although a work might address specific issues, it should not be a problem to solve. It should ideally incorporate the questions and the answers, along with the labor and the emotions that went into it, into a unity. It should be its own new thing, confident and whole.

The work of video and sound artists Angel Nevarez and Valerie Tevere, currently on view at the Institute for Contemporary Art, is extremely ambitious. It considers different ways in which people can use music and sound, and about how that can relate to urban space. Less directly, it also deals with artistic obsessiveness: the formulation of odd ambitions and the will to realize them.

In Touching from a Distance (2008), we see a mariachi band performing a Joy Division song in the main plaza of Guadalajara while a demonstration against public corruption unfolds all around. In We Need a Theory to Continue (2008), three Austin, Texas, bands perform songs they wrote to the artists' lyrics on three side-by-side screens. "Persistent voices," they sing, "culminate from beyond the event-horizon / With tonal clarity/ Repelled by dogma. . . ." In the cacophony, you can't really make out what they are saying, which may be just as well.

Blinded by the Sight (2013) shows the Charles River filled with small sailboats and the Boston skyline behind while an elevatorish melody plays. If you look closely, you can see flashes coming from a building, which turns out to be Morse code for the lyrics of Siouxie and the Banshees' song "Into the Light." It might be diverting if you saw it while waiting in an airport, for example, but in a gallery where expectations for aesthetic stimulation are high, it is not so much blinding as soporific.

"Why?" I asked. "Why? Why?"

Actually, I was not so much in the dark about why they did it, because explanations of the pieces, larded with critical theory, can be found on the exhibition's wall labels and handouts. Really, what I was asking was why did they bother to do projects that were so hard to execute and offered so little payoff? And why should I bother, or bother you about it?

Then I turned a corner and discovered the final piece, Memory of a Time Twice Lived (2015), filmed in Philadelphia and in Mexico. My first reaction was that I had stumbled into some French New Wave cinema from the 1960s. A woman, presumably Tevere, is in Mexico, talking with a museum curator about a T-shirt featuring the image of El Santo, a celebrated, silver-masked wrestler. She shows him a still from Chris Marker's 1962 film La Jetée, in which a man is shown wearing the shirt, and he tells her that the shirt "does not exist."

This is followed by footage about the amazing career of El Santo, who, during his midcentury peak, sold a million comic books a week and also starred in movies. The curator tells the filmmaker about El Santo's death and the unlikely rescue of his belongings, but he wonders why she is so interested in a T-shirt.

Later in the video, we see a man in an El Santo costume moving about Philadelphia. He shows up where people are posing with the Rocky statue, and in other locations. Then there is a Mexican accordionist playing with the mural of former Mayor Frank Rizzo, in what many Philadelphians anachronistically call the Italian Market. This tableau dramatized the shrinking stature of the outsize politician as years pass and new groups of people arrive and bring new meanings to old places. Finally, we are in the Wagner Free Institute, among the stuffed animals caught in the middle of action, like the striking still images used in Marker's film. A mariachi band plays.

Not everything here makes sense, though the artists' theme of how people in different places and times change the meanings and emotions associated with cultural artifacts comes through clearly. Unlike the other works, which seem to be explorations of theory, this messy, sensuous, funny, yet serious film feels like it needs to be. I am grateful for the desire that brought it into being. I don't ask why.

The cavernous multistory exhibition space in the ICA's ground-floor gallery presents an opportunity and poses a challenge for every artist who shows there. Designed at the end of the 1980s, when works of art seemed to be getting ever larger, it seems to signal to artists to go big or go home.

The current exhibition "The Black Show," by Los Angeles artist Rodney McMillian, makes the slyest, most theatrical use of this space I have seen. First, he places Many Moons, a 70-foot-long painting made for this exhibition, diagonally across the exhibition space, walling off our view of the high gallery. The work, which straddles the line between painting and sculpture, is a thickly painted scene, apparently of a forest, though it also looks bloody and visceral. (McMillian seems to have learned his sewing technique from Dr. Frankenstein.)

Punctuating the space are video screens on which the artist appears. On one, the artist appears as a preacher giving an unorthodox sermon about death as the gift of God, while on another, he is a masked, costumed science-fiction figure in a large coat, riding the New York subway and dancing in the street in Harlem. On the wall are black vinyl sculptures, including a pair of lungs, and one called Wizard (for Doro), which evokes the angular tailoring of a Ku Klux Klan costume, only in black rather than white.

The overall effect is menacing. What could he be hiding behind that wall?

Spoiler alert: There's not much there - only a video of the artist in a simple cabin, reading a story from Winnie-the-Pooh. He is intimate and charming, occasionally holding up the book to share an illustration with us. Perhaps that scary forest is really just Pooh's Hundred Acre Wood.

The strength of this show is not in its individual works, but rather in its creepily ambiguous environment, one that forces viewers to think about what they expect - and why.

TWO AT ICA

Angel Nevarez and Valerie Tevere
Through March 27.

Rodney McMillian: "The Black Show"
Through Aug. 14.

At the Institute of Contemporary Art, 118 S. 36th St.

Hours: 11 a.m. to 8 p.m. Wednesday; 11 a.m. to 6 p.m. Thursday and Friday; 11 a.m. to 5 p.m. Saturday and Sunday.

Admission: Free.

Information: 215-898-7108 or www.icaphila.org