I received a lot of email and Twitter feedback in the wake of my overview of the Spotify service, which is either the greatest music service of all time or a tired retread of what came before, depending on your perspective and experiences. As is always the case with hyperbole, the truth is somewhere in the middle of these two extremes, I think, but I do feel there are two interesting trends emerging not coincidentally with the release of Spotify in the US.

The first is that Spotify appears to be an "it" service, one that succeeds despite the fact that others--Zune Pass, Rhapsody, whatever--pioneered in the market in question. Other examples of such "it" products and services are Google Search, Facebook, and even the iPod. Sometimes, certain products and services just reach a critical mass, in both usage and mindshare, and for whatever reason--and no, not always because they're "better"--just succeed where others failed. As consumers, it's important to identify these things, and make the right bets.

Second, with the digital music market bifurcating with the introduction of useful new services, we now have more choices than ever before, not just between the actual services themselves, but also between the types of music services we can access. I mentioned this in my Spotify overview, but I'd like to elaborate a bit on this second theme now. Based on the feedback I'm getting, I can see that there's a lot of confusion out there. But this isn't like the Microsoft vs. Apple wars of old, where there has to be a single winner. If you're a digital music lover and an avid consumer of this kind of content, it's likely that you'll want to use two or more of these services in tandem. And there is absolutely nothing wrong with that.

To reiterate and expand on what I wrote in my introduction to Spotify, there are basically three types of digital music services available today. These are:

A la carte music services. When most people think of music services, they think of iTunes, which is a traditional, a la carte music service. That is, iTunes offers only paid music, per song or per album, and no subscription offering. Apple CEO Steve Jobs has argued that consumers want to "own" their music, and consumers have responded in kind by purchasing over 10 billion songs from the service since 2003.

There are issues with such a service, however. Many a la carte services, including iTunes, don't make it easy to reclaim previously purchased music. When you buy and download a song, you're expected to manage it, copying it to other devices and backing it up. And if you lose that song file, you'll typically (but not always; this varies by service) need to contact customer service, hat in hand, and ask for a redownload.

Beyond this basic issue, you're also responsible for managing your collection of music, and if you want a tailored experience--certain songs playing in a certain order, say while working out at the gym--you will need to manually create your own playlists. Or you can utilize a feature like Genius in iTunes (or Smart DJ in Zune) that will examine your collection and create more dynamic playlists that are based on a song, artist, or genre. (Capabilities vary by service.)

In the past, the types of portable devices you used determined which music service you used. But with a la carte music services moving to DRM-free files years ago, this is no longer a concern. Any song you buy from any service today (Amazon MP3, iTunes, Zune, whatever) should play just fine on any modern device (iPod, iPhone, Zune, any smart phone, and so on). So it's possible within this realm to mix and match. You could be a diehard iPod user, for example, but purchase music exclusively from Amazon. The compatibility issues of the past are long gone.

While your mileage may vary, I happen to utilize two a la carte music services regularly, Apple iTunes and Amazon MP3, in that order. I look to iTunes first because it offers the highest quality music files, 256 Kbps AAC, though Amazon MP3's high-quality MP3 files are pretty close. It's worthwhile utilizing at least two services and comparing prices whenever you want to buy something. You never know, one or the other may have what you want at a significantly lower price for some reason.

Digital radio services. Services such as Pandora, and related services like satellite radio, offer streaming radio-like experiences on the web, on PCs, and on compatible mobile devices. While these services are typically seen as paid, subscription-based services with a monthly or annual fee, many offer more limited free versions as well.

Digital radio services basically emulate traditional, FM radio stations, but with a twist, and via Internet-based streaming. So there are genre-based stations (Today's Hits, Classical, Rock, and so on), which is very close to what you get on the FM dial, but also dynamically-created stations that are based on your favorite artist or song. So you enter such an entity into a field, create your station, and then listen to it. When you hear songs you like, you can tag them as such, and vice versa, and over time Pandora will hone its stations to better match your needs.

This type of service requires a little or a lot less work than a traditional music service, depending on how much you want to micro-manage what you're hearing. But unlike with a traditional radio station, when a song you don't like comes up, you can tap "Next" and skip it (though this capability is somewhat limited, especially in the free version of the service).

When you pay for Pandora, via the Pandora One offering, you get better quality (192 Kbps) streaming music, access to a real Windows desktop app (and not just a web interface),  unlimited listening (vs. 40 hours per month in the free version), and, best of all, no advertisements. It costs just $36 a year, and perhaps not surprisingly, I do pay for Pandora One.

Of course, once you get into a streaming model, you are introducing DRM as well, and thus Pandora and other services aren't universally compatible. So you'll want to ensure that a compatible player is available for the device types you're going to use. In the case of Pandora, this means all the big players: iPod/iPhone, Android, Blackberry, Palm Pre, and Windows Mobile. (Hopefully, a Windows Phone version is on the way as well.)

Interestingly, Pandora support is also being built into many new automobiles as a nice alternative to satellite radio. This includes new BMWs, Fords, Mercedes Benz, and other automobiles, with more on the way. I noted earlier the notion of "it" services. In the case of digital radio services, Pandora may just be that service.

Digital music subscription services. Finally, we also have a third category of music services that neatly splits the difference between the first two. These paid music subscription services offer customers unfettered access to enormous music collections in the cloud, as long as their accounts are up to date. But they work more like traditional a la carte music services in that the user is basically responsible for manually finding music, creating playlists, and so on.

Examples of these services including long-time players like Rhapsody and Zune Pass, and the latest entry, Spotify. Each comes with a monthly subscription fee. Each offers access to several million songs. Each lets you build playlists. And each has at least one offering where you can download or access your subscribed content from one or more compatible portable devices.

Where these services diverge is in accessibility and device support. With Rhapsody ($10 to $15 a month), you get a native Windows app, web access, and compatibility with numerous MP3 players and smart phones, often via native apps in the latter case. (This includes Windows Phone compatibility, too.) You also get compatibility with some interesting home theater equipment, including the popular but expensive Sonos devices.

Zune Pass is perhaps the best offering of the three, until you factor in device compatibility. It costs $15 a month, yes, but that fee includes 10 free DRM-free MP3 downloads each month, so if you're actively buying music regularly anyway, the net cost here is just $5 per month, a bargain. Zune Pass is compatible with PCs and via the web, but only with Zune devices and Windows Phones. Zune Pass is somewhat accessible on Microsoft's own Xbox 360, too, which should put this service over the top for some. But the support is limited to Smart DJ playlists or manual search and play; it offers no way to create and manage anywhere-accessible playlists in the cloud. Zune Pass does not work with any of the world's most popular devices--iPhone, Android, iPod--and is thus a nonstarter for many.

Spotify, as I noted in my separate overview, offers a nice Windows application and can integrate with your PC-based music collection for better performance. There are two paid versions, one for $5 a month and a second at $10+ per month that adds mobile device support. Currently, this means iPhone, iPod touch, Android, Symbian, Palm webOS, and Windows Mobile, though a Windows Phone app is on the way.

I move in and out of Zune Pass pretty regularly (you can stop and restart the subscription, easily, at any time), and I'm currently still using and testing Spotify. Which of these you use, if any, should depend as always on your usage, and which devices you use. If you have an iPhone, for example, Zune Pass isn't an option.

But wait, there's more

OK, so there are these three basic music services types. But here's where things get truly interesting. Because when it comes to digital music, you aren't limited to just these offerings and you certainly don't have to pigeonhole yourself into just one of the services types.

For example, I use Windows Phone and an iPod touch, and of course Windows PCs. And as I noted above, I use iTunes primarily for music purchases, but I also use Pandora for streaming radio. The reason is simple: While I sometimes do want very specific music, I also sometimes want a customized mix of songs as you get on the radio, a mix that will contain surprises both good and bad. That is, the iTunes purchases are typically for music that I'm already familiar with, but Pandora is for discovering new (or new to me) music.

Things get further complicated by the rise in cloud storage and streaming services like Amazon Cloud Player and Google Music. These services provide cloud-based storage for your existing music collection, allowing you to upload that collection and store it online, for free or, for more storage, with a yearly fee. Competitors like Apple, which won't offer this capability in its coming iCloud service, claim this is an arduous and time consuming process, but I was able to upload my music collection to both services in just a few hours and, let's face it, you only have to do it once. (Utilities will continue to monitor your PC's music collection and upload new songs on the fly.)

(By the way, I'm still using both Cloud Player and Google Music, having not decided between the two yet. I may simply continue replicating my music collection in both places going forward.)

And once your music collection is in the cloud, you can stream it to the PC, or to compatible devices, much as you would with a digital music subscription services. The difference is that you're accessing your own collection. But it's also free or much less expensive than a typical digital music subscription service, and by putting that collection in the cloud, you're making it more universally accessible and removing the need to manually copy your collection from PC to PC and from device to device.

Well, except for one thing. For all the nerdvana we're experiencing here, there is one major wrench in our plans to finally remove our need to micromanage our music collections on our own devices. And that's because wireless carriers are starting to cap monthly bandwidth on mobile devices. So while the notion of continually streaming music--be it from Pandora, Spotify, Zune Pass or whatever--over 3G/4G wireless networks may seem like a good one, it's unclear what this consumption will do to our ever-dwindling monthly bandwidth allotments. For those with unlimited plans--for now--this isn't an issue. But I could see it becoming an issue as we move more and more of our content--not just music--into the cloud.

Whichever strategy you pursue, just remember this: Things are always changing, and the available services are expanding up and out to include new capabilities and device compatibility. And there's no reason to settle on just one service. Sure, you may love iTunes for whatever reason, but you may also want to bolster your own collection with a digital radio or music subscription service. The choices are out there, you just need to examine your own wants, see what's available, and choose accordingly. There's never been a better time for enjoying music at home, work, or on the go.