Now that I've had my iPhone for a few months, I'm trying an experiment to see if I can't replace the laptop I carry around with my iPhone + internet connected computer. To this end, I've been trying to find a program that will let me play the music on my iPhone through the hardware and software on the host computer.

If I recall correctly this was possible a few years ago with the iPod - Linux software like Rhythmbox and Banshee was able to read the music off an iPod and play it through the speakers. I even thought I recalled iTunes itself being capable of this at one time.

Now, however, iTunes greys out/disables the music on my iPhone and I can't find any documented support for the iPhone in any other music program. Is this really no longer possible? Am I limited to using the headphone jack to get music to play?

(note: I am using an iPhone 3G with the 3.0 software. I am attempting to play music on computers other than the one I sync with)

Several replies mention that I should check "manually manage" to do this. I just tried this on a computer that I don't sync my iPhone to and it asked me to erase and sync, which is obviously something I don't want to do.

update: OK, I checked the "Manually manage music and videos" box on a computer that I didn't sync to (now known as "Computer A"), and it told me that I needed to erase & sync to cause the changes to have effect, so I did. At this point I'm guessing that my iPhone thinks that it's syncing with that computer. I copied over a few songs using the autofill feature. At this point, Computer A sees the maybe 10 or so songs I've copied using autofill.

I then plug my iPhone into my Macbook ("Computer B") which I've been syncing with. At this point, I'm pretty sure that it still thought that all my synced content was still on my iPhone. The "manually manage music and videos" checkbox isn't checked, so I check it and go through a similar process where iTunes erases the synced content and I copy over a playlist. At this point, there's no trace of the songs that I copied over from Computer A.

So I plug my iPhone into Computer A - in the Music section are the handful of songs that I had copied over earlier, greyed out and unplayable. To make sure that this wasn't some sort of caching issue, I plugged my iPhone into my sister's Macbook ("Computer C") and it lists the same few, greyed out songs that I had copied over from Computer A.

Plugging into Computer B doesn't reveal these songs at all, only the songs that it copied over (these are playable).

A few things:

• This inconsistent behavior is driving me insane. Why would my iPhone report two versions of its contents to different computers?
• Is there a way to get a computer to completely forget about an iPhone and just resync everything to get everything into a consistent state?
• Even if I get the phone into a consistent state, I still can't play the files on my phone anywhere but the computer I sync with, which was my original goal. What am I doing wrong?

maybe I should read the fine print before I mess with my iPhone

So going over this thread with a fine-toothed comb again yields this lovely tidbit in the Apple docs:

OK, so manually managing is a dead end on the iPhone. Are there any other options? Any unofficial third-party programs or drivers that will work?