Like as an audio file or something? So far all I've been able to do is take a vid of my TV with my phone and upload it to YouTube and the sound quality is atrocious. I'm not very competent with computers so ELI5, please.

I've tried recording from my TV that my PS3 is plugged into to my PC by plugging a 3.5mm to 3.5mm cable (3.5mm is what most headphones use, if you need to know) in the headphone jack of my TV and plugging the other side in the line in of my PC (usually Line In is the blue headphone jack on your PC). Then i set up my microphones for recording (right click the volume change icon on your desktop > recording devices (i use a Dutch PC and i'm not sure what things say in English, sorry if this is a sloppy translation) > then turn off all your microphones but Line In by rightclicking them and turning them off/on), and went in Audacity to record.

Problem is that this method causes a lot of noise, at least for me. The TV changes the volume so that it's controllable. If you'd record from your TV when it's on 20, your recording's volume is going to be on 20 out of 100. I'm not sure why, but recording to PC with headphone jacks and cables always creates a small bit of noise for me, which you obviously don't want. Noise always stays at the same volume, so let's just say that it's on 10. If you'd record with your TV's volume on 20, the background noise obviously being on 10, then if you would amplify it from 20 to 40, the background noise will also amplify and change from 10 to 20. To work around this you can set your TV to full volume, so let's say 100. This minimizes the background noise as it stays on 10. But if you're not cautious that could lead to some major ear r*pe, so i haven't tried going on full volume yet. I'd rather not use this method (although it's probably the easiest and cheapest).

I've also been told to try connecting a PS3 component cable to an RCA to 3.5mm cable (haven't tried this yet, but since it will take the audio straight from the PS3 instead of from the TV there most likely isn't any noise), or even to just buy a capture card and record from there (Shadowriver, the guy behind LittleBigAudio does that too. I didn't yet. Capture cards are expensive..). Obviously both of these methods cost a bit (or a lot) more money. Probably worth it though.

yea. I've heard that having a proper audio capture set up is the only way to go for quality. But if your talking about lbp2 music, I wouldn't worry about having audio capture. The music sequencer music is only 16bit audio ( that's what I've been told anyways ) and this means that things are already compressed muddy. if it were me, I would probably just get an RCA to 3.5mm adaptor like woutery was talking about. That shouldn't be too expensive.

Just saying, i don't have an RCA to 3.5 cable... not even a component cable. I've just been told this and i sourced my info from how the cables are connected.

Option 1: (Best quality)
If you're already an invested musician you probably have an audio interface. If you don't, but want to get into music in the future, buy one. (Focusrite and M-Audio are great starting brands.) Buy an RCA (Female) to TRS or XLR (male) Most interfaces have a combination TRS/XLR jack for their inputs, so either should work. Then adjust your PS3 Sound Output settings to relay your audio via component cables. Then use the RCA cables from the PS3's component out snake, (Red/White ones) plug them into your conversion to XLR or TRS, plug into your interface and into your computer, then record with your DAW. (WAY Better than RCA to 3.5mm)

Option 2: (Good quality)
Get a capture card for your television. Most of these will capture in HD video, but have audio quality that rarely gets at 44.1k and 16 bit resolutions. (Bare minimum of decent quality, what you'll get above) That being said, you can use them to record and you'll get reasonably good quality from it. (It's what LBAudio uses)

Let me know if you need help!

oh snap! you hear that LBA? better start recording with option 1

I'm not an expert on recording things either. I never really had much I had to record

Figured I would drop this bomb here.
Just a lil' something I thought of to record music..

If you get the ps4 version of LBP3, in theory, you should be able to press the share button and upload your game footage to Youtube. Then, hop on the pc, and download a video editor, a video to audio converter, and a program that can download videos from Youtube.
Download your game footage off of Youtube, and then edit it down to just the song, then convert the video to an audio file of your choice.

Boom

Ofcourse you can do that

Upload your video to YouTube, and this site will do the rest:
http://www.clipconverter.cc/