When we hear the word “opera,” we generally think big: big orchestra, big stage, big tenors and sopranos, big ticket prices. A couple of Portland shows last week made useful reminders that the genre can work at smaller scales and with non-traditional forces.

Friday night’s Electric Opera Company (EOC) concert at Portland’s splendidly restored Alberta Rose Theatre, like every show the multi-guitar-keyboard-and-drums outfit stages, sets out to show that classical music — some of it, at least — can resonate with contemporary listeners who will open themselves to it, by presenting the same tunes, note for note, played on the kind of plugged-in instruments most of them grew up hearing. Perform Mozart on instruments a pop music lover is used to hearing rock bands play, EOC front man Bobby Ray’s theory goes, and they’ll be open to the music’s beauty, not put off by what may seem a stodgy means of delivery. It’s the converse of the Portland Cello Project approach: Instead of playing non-classical music on “classical” instruments, the classically trained musicians of EOC play classical music on non-classical instruments.

EOC’s opening act, Classical Revolution PDX, shares the goal of bringing new audiences to classical music by removing superficial, non-musical barriers. In CRPDX’s case, it’s not the old instruments but rather antiquated venues and stuffy performance rituals. When CRPDX’s musicians perform in a theater instead of club, though, it’s hard to avoid applying the standards used for professional musicians who stand onstage and demand full attention, and the performers’ enthusiasm and informality can’t always make up the difference. Stage performances also make me want to know things seldom provided this night, like the names of the performers and the pieces being played.

Opening a concert like this with a long, unidentified virtuoso showpiece (Tartini’s famous “Devil’s Trill” sonata) can be rough sledding for any audience with 21^st century attention spans, no matter how well played. More contemporary fare fared better. Flutist Celine Thackston’s breathless version of Ian Clarke’s exercise in extended techniques, “Zoom Tube,” would have impressed Jethro Tull’s Ian Anderson. PCP/Vagabond Opera/ solo artist Ashia Grzesik’s set profited from her stage charisma and vocal/cellistic chops — she’s a Portland star on the rise. Grzesik’s version of Dolly Parton’s “I Will Always Love You” almost cleansed Whitney Houston from my memory. I wish trumpeter David Binnig had been identified so I’d have known who to thank for the hypnotic foot pedal looping enhanced original, “Dies Irae.”  Classical Revolution PDX is always welcome, but so far it tends to work better in less formal settings.

Electric Opera’s set certainly established the lanky Ray as a star — if he wants to be. He’s got the vocal and guitar chops, stage presence to burn, a real musicality, and an earnest, visible affection for the music he’s covering, from Mozart to Tchaikovsky to Chopin. His sly humor and strict preparation kept the show moving and fun, without getting caught up in instrument tuning and set changes. But he’s also got too much of a sense of humor and irony to wallow in rock star cliches, instead parodying the guitar god moves in an understated Spinal Tap fashion. Even the spectacular drum solo worked as both impressive showcase and dig at rock star cliches. Like David Byrne, Ray is able to wink at the excesses of the music he loves without smirking, so EOC shows effectively strike that difficult postmod balance between laughing at and loving its subjects.

Although it was billed as a “devil music” show (which was more appropriate when they did it at Halloween), the concert packed only a few demonic references and, except for some Bizet and Gounod, not even that much opera. Keyboards and drums — all played adeptly — were as prominent as guitars. When Classical Revolution’s players crowded the stage with EOC, rare treats like the Beatles’ “I Am the Walrus” became possible and delightful. The affectionate/satirical attitude culminated in a clever Lynyrd Skynyrd-meets-Led Zep mashup of those two most cliched and overplayed of  ’70s perennial rock encores that long ago became jokes, which Ray dubbed “Stairway to Freebird.” EOC probably appeals more to rock fans than to many hard-core classical types, but it’s hard to imagine any music lover coming away from any of their shows without a grin and a deeper appreciation for the music, or the musicians.

On Wednesday, Cascadia Concert Opera returned for its third Portland appearance in as many summers in a minimalist, hour-long brown bag lunch performance of Mozart’s sly opera Cosi Fan Tutti (All Women Are Like That). The group, comprising professional Oregon classical players from Eugene, Corvallis and beyond, also performs in alternative venues such as nursing homes, community centers etc. in Eugene, the Oregon Coast and elsewhere.

How do you cram a whole opera on the little stage at downtown Portland’s The Old Church (the site of this show) or Sherman Clay/Moe’s Pianos store (where they’ll play September 18)? Strip it down to a few singers playing major roles, and a single, very busy pianist, that’s how.

When the composer is history’s greatest melodist, Mozart, whose sublime music depends far more than most on the pure power of the tunes rather than orchestration, spectacle or even plot, it can work just fine — if the singers are up to it. These were, and their theatrical skills — particularly hilarious hammy tenor Nick Larson — matched their vocal prowess. Even their non-verbal reactions were compelling. Of course this was a different world from Portland Opera’s excellent full scale staging of the piece last year. But with only a few props — a sword, a mustache, an apron, various headgear — and a piano, some strong singers, and of course some of the most achingly beautiful music ever written, Cascadia Concert Opera, like Classical Revolution, Electric Opera and other Oregon alt classical stalwarts demonstrate that in the right hands, there’s no reason to confine classical music to its traditional venues — or audiences. And that opera doesn’t have to be grand to be good.

Cascadia Concert Opera’s Cosi Fan Tutti continues next month.