What exactly makes a group a "power trio" in your opinion?

I’m not stating the overwhelming majority of bands are such, even when 100% of the actual bands I’ve been in were. It may be a 60 % majority in the bigger picture, but the concept of a band having a guitarist, a bassist, a drummer and a vocalist is archetypal to rock music, extremely common and as such would render the power trio monicker diluted to the point of homeopathic water.

It’s pretty tough to get even a cohesive guitar/bass/drums/vox group together, IME. A bigger group would have been a nightmare to assemble! It may well be that at the garage / local band level this composition is more common than with established, world-famous groups who have (had) both the allure and the means to get a larger group going.

Off the top of my head, Led Zeppelin, Black Sabbath, Queen, U2, REM, the Who, Ramones, Sex Pistols, The Clash, RATM, Bon Jovi, Van Halen, Def Leppard, Nazareth, Extreme, Living Color, Motley Crue, Poison, Blur, Oasis, Soundgarden, Alice in Chains had one of each.

At any rate, we’re back to the definitions of if the singer also plays an (occasional) instrument, is she an instrumentalist?

You may well be right—and this goes back to @Si_Amigo’s point:

Yes, but the concept of a band having two guitarists (lead and rhythm) is also archetypal (cf. The Beatles, The Rolling Stones). And there are many bands with a dedicated keyboardist.

And it’s entirely possible that one or both of us have our perceptions skewed by the type of music we like to listen to. If you like the “rawer” sound of guitar-bass-drums and I like the “fuller” sound that comes with adding a rhythm guitarist and/or keyboardist (or a sax player, or something else like that), that may well influence which bands spring to mind most easily.

Doesn’t a “pop trio” usually boil down to one person who can sing and front a band and handle lead and rhythm guitar duties at the same time? I know in a few cases it’s the bass player (The Police, Rush, etc) or even the drummer but the success of the band is usually some genius (usually the song writer) with two mere accompanists. The list of trios making equal contributions (like Cream or, again, Rush) is very rare.

Nope, my understanding is the trio mean three. It’s that simple.

Oh, I’m not disputing that, just talking about how the “power trio instrumentation,” with or without a separate fourth person on vocals, is typical of garage / local bands.

Vocals is basically another instrument, so if you add a vocalist you are no longer a trio. I’d go so far to say that the vocals are the most difficult part of any band, which is why so many groups have to have a separate vocalist in order to be successful.

If Pete Townsend had more confidence in his vocals in his youth the Who would have been a power Trio band. But they needed Roger, which knocked them out of the power trio band category and put them in with “the rest” of the bands. It’s not a negative to be a regular band, but people shouldn’t be pushing the meaning of trio.

Blue Cheer!

I’ve seen those guys. Quite entertaining!

I am surprised no one has mentioned Nirvana. The group had three members–are they considered to be a “power trio”?

Most definitely! Good catch!

(for proof, just listen to the “Live At Reading” album. Most powerful.)

Yes, how could we have missed an albino, a mosquito and my libido?

At the start, sure. After Pat Smear joined, no.

Huh. Somehow I never noticed they had an extra guitarist on SNL. I guess he toured with them for six months. I had no idea.

If we’re just name checking awesome power trios. I give you the TOY DOLLS!!!

When I hear “power trio,” the first thing that comes to my mind is straight up rock or (even better) “hard rock.” This is based on hearing the term for years. YMMV.

I don’t understand this post. If there ever was a band that was straight up hard rock (or punk rock, but that’s not much of a difference), it was Nirvana. I’m just listening to “Live At Reading”, and it blows my ears and mind just like Cream and the Experience, maybe even more so.

How does it work if a band has two lead guitarists, like Def Leppard?

Then they are not a trio since they have a bass, drummer and singer as well.

What is so hard about the concept of there only being three people in a trio?

Not picking on any one person, but it astounding how many people think there are exceptions.
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A bit off topic, but ehhhh… I dunno. Yea, grunge is technically “rock.” But - based on my experience only - the term “power trio” is most commonly used with three piece bands from the 70s and 80s who play “high energy” or “hard” rock.

I don’t know how to express this diplomatically, but may it be that you’re older than me and it’s a matter of age? I was 23 when Nirvana broke, and I took them as a power trio just as I had embraced the Police 12 years earlier as a 11 year old. Classic power trios like Cream and the Experience I had discovered after listening to the Police and before Nirvana broke.

And on review, you cannot deny that Nirvana also played “high energy” and “hard”.