On songs that lack a keyboard part, "Rock Band 3" will let you play the guitar or bass parts on the controller.

Over the past nine months, conventional wisdom has turned on music-based video games. What once was seen as another new genre that would take its place alongside platform-jumping games and first-person shooters has started to look more like a fad. Middling sales of “The Beatles: Rock Band,” “Guitar Hero 5” and more kid-oriented fare like “Lego Rock Band” and “Band Hero” have left those of us who still try to host the occasional “Rock Band” party wondering if our friends still enjoy playing, or if they’re on the verge of shunning us, like they would if we repeatedly invited them to partake in some passé activity like swing dancing.

OK, that might be overstating things a little, but if there’s one video game developer who can make us party like it’s 2008 again, it’s MTV-owned Harmonix Music Systems. The studio that created  “Guitar Hero” and “Guitar Hero II” before moving on to the four-player format with “Rock Band,” with apologies to current “Guitar Hero” developers Neversoft, has been the biggest innovator in a genre that could use a little shaking up.

During my trip to the game industry’s annual E3 expo in Los Angeles last week, I got a look at some of the new features Harmonix has planned for “Rock Band 3,” and came away feeling like I’d just seen the best game at the show.

Headlining the list of new features are the addition of keyboards and the incorporation of vocal harmonies, first introduced last year in “The Beatles: Rock Band.” The new instrument and two extra vocalists bring the maximum number of simultaneous “Rock Band” players to a staggering seven, something we saw when the curtain went up on Harmonix’s presentation and revealed seven people jamming out to Huey Lewis and the News’ “Power of Love.”

Of course, the first song just about anybody thinks of when they hear about the seven-player setup is Queen’s “Bohemian Rhapsody,” and it’ll be in the game when it ships. But the addition of keyboards should open up such under-explored genres as the prog rock of Yes and King Crimson and the new wave stylings of Depeche Mode and New Order.

The new "pro" difficulty modes can teach you how to play real instruments.

For actual musicians left underwhelmed by the way previous “Rock Band” and “Guitar Hero” games have simplified their craft into timed button presses, “Rock Band 3” will include a feature they’re calling the “pro” difficulty. With the use of a special adapter, you’ll be able to plug any MIDI-enabled drum kit or keyboard in and just play along with the song, using a different note chart used only in pro mode.

Guitar players and bassists will be able to play a specially designed Fender Stratocaster with actual strings, though no release date or cost has been announced. (Another, more traditional-looking pro controller with dozens of buttons along the neck will also be available.) The demo’s “eureka” moment came when a developer plugged his guitar into an amp so we could hear him play along with the game.

While no one will confuse pro mode with guitar lessons, it should put players well on their way to learning a real-world skill, rebutting the naysayers who think these kids playing “Rock Band” would be better off learning a real instrument.

As someone who’s comfortable in my musical ineptitude, I don’t expect to get much use out of pro mode, though a number of refinements and minor-sounding features are worth getting excited about. An overhauled menu system means that each player controls his own in-game minimenu. In other words, if my overzealous friend Jonathan starts flailing away on the drum kit while the rest of us are taking too long to pick our next song, it’ll no longer send the entire group back out to the main menu. A sheepish Jonathan will just have to rejoin the rest of us once he realizes he’s drummed himself right out of our band.

Lastly, “Rock Band 3” will include a number of new ways to sort through our ever-growing library of songs. (The folks at Harmonix estimate there’ll be 2,000 songs available by the time “Rock Band 3” releases.) In addition to gaining new categories for filtering songs, we’ll be able to rate tracks on a scale from zero to five. Just like they would on your iPod, high-rated songs will come up more often on the randomly generated setlists. If you rate a song at zero stars, you won’t hear it unless a challenge specifically requires it. What’s more, the filters will be stackable, so you can make a playlist of all easy songs from the 1980s that feature vocal harmonies. And the ability to save playlists and access them in later sessions will hopefully cut down on the time spent in the menus when you host your first party.