We’ve had “Rock Band” for a few weeks now, and some questions have arisen.

We at Multiplayer like “Rock Band” (and we’d be saying that even if it wasn’t published by MTV Games), but even the finest games beg some questions.

For one, we found out that a player’s avatar can only play one instrument. If you create the world’s coolest drummer, that drummer will never be able to play the guitar — not once. Another thing we noticed was the lack of an online play mode for Band World Tour, meaning that any bands we formed over the holidays can only reunite in-person.

So what gives? Amid the PS3 guitar compatibility wars, Harmonix Senior Designer Dan Teasdale (who I met when I visited their offices in October) spoke to all our questions via e-mail. Regarding the one-instrument-per-avatar policy, Teasdale said:

“A lot of this falls into how we create and track progress with our characters in ‘Rock Band’ - allowing your drummer’s progress to affect your guitar profile starts getting messy when you’re worried about stuff like difficulty curves, and having drummers wear clothes that might be too bulky for someone sitting behind a big drum kit and animating wildly is a problem too. We do hear that people want to be able to have their character play all instruments, and surmounting these hurdles is something we’re looking into.”

Read on for more on Band World Tour mode, the future of downloadable content and why we don’t have any Led Zeppelin songs yet…

Multiplayer: What is the function of the battery case on the back of the wired Xbox 360 Fender Stratocaster guitar?

Teasdale: On the wireless Xbox 360 Fender Stratocaster that we’ve announced, it holds the batteries! For wired controllers, it’s a side effect of us using the same backing plate for wired and wireless models. Some of our community members on Rockband.com have come up with novel uses for it though, including adding more weight to the guitar for those people who prefer heavier guitars.

Multiplayer: There were manufacturing flaws in the guitars, which Harmonix has said it identified and fixed. Are they already through with that batch? Or are guitars with the flaw still potentially being sold?

Teasdale: The flaws with some of the early guitars were limited to that initial day one batch. Since “Rock Band” sells out in huge chunks of the U.S. on the same day as we ship stock in, it’s a small-to-none chance that these guitars are still on shelves. Naturally, if you have any problems with your instruments, you should contact EA who will replace it free of charge in 60 days.

Multiplayer: Why can’t you have one avatar play multiple instruments?

Teasdale: A lot of this falls into how we create and track progress with our characters in “Rock Band” - allowing your drummer’s progress to affect your guitar profile starts getting messy when you’re worried about stuff like difficulty curves, and having drummers wear clothes that might be too bulky for someone sitting behind a big drum kit and animating wildly is a problem too. We do hear that people want to be able to have their character play all instruments, and surmounting these hurdles is something we’re looking into.

Multiplayer: Why is there no online for the Band World Tour mode? If you can link up with your friends for a four-player quickplay session online, then why not for a series of four-player World Tour sessions?

Teasdale: The big thing stopping us from shipping Band World Tour Online on the disc was dealing with persistent bands, and it was a heartbreaking thing to have to hold off on. It’s one thing to play a quickplay game online, but it’s another whole layer of complexity to have campaign data synchronized between multiple players, have multiple people’s progress stay in sync with Rockband.com when people are missing, kicking people out of a band when they’re not on the same console and not online — I could go on, but it’s a massive minefield to get working right. Having said that, it is something we’re very actively looking into.

Multiplayer: Why aren’t there any songs from Led Zeppelin or AC/DC or Pink Floyd or The Beatles? Can we expect them in the future? (Pretty please?)

Teasdale: You’re preaching to the converted here! I’m from Australia, so it’s part of my citizenship requirements to get as much Acca Dacca into the game as possible. We’d love to get these kinds of mega-famous bands into “Rock Band,” but securing licensing and such makes this something that takes a lot longer than other artists.

Multiplayer: Can you tell us anything about Metallica debuting a single in “Rock Band”? How did that come about? Was it difficult to convince the band to do this?

Teasdale: I think it’s a natural extension of what we want “Rock Band” to be. Our goal at Harmonix is to let non-musicians experience music, and having content released for “Rock Band” on the same day that you can download it from somewhere like iTunes or buy it in a store is the next big step in the goal of having “Rock Band” be the means in which people experience and enjoy music together. It’s always tricky working out licensing terms, but as soon as we’ve shown artists the game running, they instantly get the potential in what we’re trying to do. That hard part is no longer a problem [once] these real life legends pick up some sticks, a guitar or a microphone and start belting out songs.

Multiplayer: Are there any plans for downloadable items in character customization (clothing, hairstyles, tattoos)? Officially licensed band merch (i.e. a Coheed & Cambria T-shirt)? Any more game modes, cities, etc.?

Teasdale: We haven’t announced any plans for content like this, but yes, it would be pretty cool!