How do you extend a song past its original limit?

[Guernsey]

There are some songs I want to extend to 30 minutes just like in some YouTube videos I used to watch. The thing is I don’t know how to loop them for that long let alone make sure the loop is seamless. Does anyone know how to do this? Here’s a video of what I’d like to create.:

https://www.youtube.com/watch?v=3sDFVCNFin4

[krykmoon]

You have to find a place where the song can be looped .. such as the CLEAR end of a section (or you will get a nasty cut).. then copy/paste <n> time the part you want to be repeated (adding a bit of fade in/out if it's the case.. and not always is.. it depends on the song and its flow and pattern..)

Finding WHERE and WHAT to loop is the key.. then it's merely a copy and paste operation - with minimal adjustments -

[Guernsey]

What tools can be used to do that loop?

[alex]

Audacity is a good choice to achieve this.

[ListyDoM]

ffmpeg -stream_loop -1 -i input.mp3 -t 30:00 -c copy output.mp3

30-minute loop (if you don't mind the quality of transitions)
Or do it professionally in one of the editors - Vegas, Soundforge, Audition, etc. (or the one mentioned above - Audacity)

[Guernsey]

Do those tools allow you to find where the song ends and where to start the loop again? I could look up some guides if I find any.

[alex]

Yes I would recommend Audacity as it is FOSS. You can find many tutorials online on how to perform tasks. YouTube has many video clips in DAW editing using Audacity amongst others such as GoldWave.