Before "Guitar Hero" and "Rock Band," developer Harmonix had a few music-rhythm games under its belt, and they were fantastic.

"Frequency" and "Amplitude" - among others - were the beginnings of today's rhythm-game craze, and they're still fun to play, even without fake plastic instruments.

When "Rock Band Unplugged" was announced for the PSP, I wondered how it would work. You couldn't, after all, use a bunch of peripherals.

The answer: Go back to the beginning.

"Unplugged" plays like the regular "Rock Band" as far as the notes go (with the exception that there are four notes instead of five).

The difference is that you play all the instruments yourself. At the same time.

This is done via the track hopping from "Frequency" and "Amplitude."

When you start a song, you begin on one of the instrument tracks, say guitar. The notes are divided into phrases, and if you hit all the notes in a phrase, that track continues to play on its own for a time. You then jump to one of the other three tracks, rinse and repeat.

If you're good, you get all four tracks going at once. If you're bad, tracks you're neglecting while focusing on another fail.

It works amazingly well, although it takes a little time getting used to the new button-note mapping.

The two left notes are played by hitting the left and up buttons on the directional pad. The right two notes are the triangle and circle buttons. This lets you use both hands for quicker notes.

And you'll need to be quick. It may seem simpler, but it's not. I did fine on medium, but as soon as I bumped up to hard, well … it wasn't pretty.

The game is set up just like the other "Rock Bands." You create a band and tour the world, playing gigs and earning money, fans and stars.

There are nearly as many options to customize the looks of your bandmates as in the console brethren.

Really, the only problem with "Unplugged" is it's a one-man band. There is no multiplayer, which is sad considering playing with friends is what "Rock Band" has always been about.

Still, it's great to take along on road trips, and the library of songs is sizable and expandable (for a price).

Players with fond memories of "Frequency" and "Amplitude" will definitely want to play it.

Etc., etc.

-- Can you hear me?: As you play instrument tracks, those notes are increased in volume so they're easier to hear. Likewise, if one of the instrument tracks is near failing, it grows silent, an aural cue to you.

-- Oww: I discovered I couldn't play "Unplugged" for long stretches at a time. The little PSP screen hurt my eyes after a while.

Aimee Green reviews video games for the Lincoln (Neb.) Journal Star, a Lee Enterprises newspaper.