MP3 players have come a long way since the first model (the Eiger Labs F-10) hit store shelves. They play and record all kinds of digital music, offer full noise-tweaking options, and sound better than ever; some even offer wackier features such as karaoke or FM broadcasting.

There are those who might suggest that manufacturers have run out of ideas for new features and from here on out will compete primarily via size, capacity, and price. These are the same folks who thought we should close down the U.S. Patent office at the beginning of the 20th century, under the assumption that everything worthwhile had already been invented.

A playlist for every mood
I have one simple idea that any manufacturer of high-capacity (4GB or more) MP3 players could add with a simple firmware upgrade: artificially intelligent (AI) DJs. Rather than hitting Shuffle All as I normally do, why can't I have my player create an on-the-fly playlist that's perfect for whatever I'm doing? For riding my bike home after work, how about some driving, energetic numbers? Or if I'm zoning out on the subway, perhaps a set of Hawaiian slack-key guitar tunes would do the trick.

So far, Rio leads the way in this as yet undeveloped area; the Rio DJ feature found on some of the company's players builds playlists based on what you've chosen to hear in the past and can cross-fade from tune to tune.

One possible reasons that manufacturers haven't taken the concept further is that so many songs are improperly tagged--if they're tagged at all. AI-driven DJs depend on song tags for creating their sets, so before we see really good automatic playlist generation, we'll need a way to perfect our tags en masse. ID3 tags have lots of data, but the newer ID3v2 tags look even more promising; they offer a tremendous number of fields for song information, including tempo (the BPM, or beats per minute), a "popularimeter" (you define how much you like the song), a play counter (how many times the song has been played), and event timing (the option to trigger certain events during specific sections of the song).

In order for DJs to have enough tag information to work with, online music merchants such as iTunes Music Store and tag-management programs such as MoodLogic would need to help users fill in all those fields properly. The stores, in particular, have a big incentive to do this since users would be more likely to pay for music downloads if they had assurance that the files would work with the auto-DJ functions of their MP3 players.

Once these tags are in place, the sky's the limit in terms of DJ possibilities. Here are a few examples:

Beat-matched transitions
Just as pro DJs beat-match songs together so that one fades seamlessly into the next, your MP3 player could use tempo information to align the rhythm of the two songs on either side of a transition.

Mood-oriented playlists
If tags had mood indicators on them, you'd be able to summon an instant playlist for your state of mind.

Smart song hopping
Online services such as Musicplasma show connections between similar bands or bands that were influenced by one another. How about picking one song to start with and having the artificial DJ plot a course from there, always choosing a similar band to play next (based on extensive tagging)?

Instant mash-ups
Given tempo, key, and embedded cues about when verses and choruses start or stop, the artificial DJ could instantly mix any two songs in your collection into a mash-up. Why not?

Thematic playlists
Your player could look at song titles and lyrics, then create a set in which every song mentioned an animal. Or it could give you an hour's worth of tunes in which every song contained the word red. Again, why not? We need new ways of slicing and dicing our collections.

Triggered events
Imagine your player's backlight turning on and off with the beat, flashing images of the band at certain times, or displaying key words from a song during the chorus.

Playlists from musical epochs
If the tags included information about where and when a certain album was recorded, it'd be possible to hear, say, a collection of songs from the CBGB era of New York City punk rock or a set of British-invasion bands from the sixties.

Downloadable DJs
Perhaps you could download a variety of artificial DJ sets from the Internet, each with its own playlist predilections and images, which would display on your player's LCD. Maybe "DJ Disco Stu" could seek out anything resembling disco in your collection, then "Deathmetal Dave" could come on afterward and zero in on the hardest, fastest stuff in your collection for his set. Who knows? Maybe they could even include a few choice audio phrases that would play between songs.

Virtual DJ tour
Maybe you could even create your own DJ for other people to download; you could specify certain tracks, artists, and albums that the DJ application would always play, then set parameters that would dictate themes, epochs, or subgenres that interest you. Of course, this would work only if the person who downloaded your DJ had similar taste, but there's no reason you couldn't give them a description before they begin.

Since all of these features (and dozens more) could be added with firmware, doing so would be quite inexpensive for manufacturers; they'd just have to pay a developer to write the code once. It could then be rolled out--or even sold--at very low cost to people who already own these devices and come preinstalled on new machines.

	The iPod's scrollwheel would work great for scratching and beat-matching. (Note: This iPod mixer does not really exist.)

What would be harder to create is an MP3 player designed for DJs to use for their sets instead of LPs. One possible design that's occurred to me is two iPods on either side of a mini mixer with a built-in cross-fader and a few simple effects (see picture to the right). It'd have to include new iPod firmware that would let you use the scrollwheels for scratching and beat-matching, but that'd be easy enough to develop.

I'd bet good money that, eventually, some manufacturer will take this concept to its logical conclusion and create a pocket-size, fully operational digital DJ device with audio editing, a full range of effects, scrollwheels, and everything else a DJ could desire. But before that happens, I hope we see more manufacturers following Rio's lead and experimenting with artificial intelligence and tagging so that we can have AI DJs playing our tunes, rather than settling for the old MP3 shuffle.