If ogg format is free how about the song ?

As all we know that ogg is multimedia format for free. You can visit here to know more information about this ogg format. Almost all free multimedia player already support this kind of format, so you don't have to worried about this. You don't lose any technical quality with Ogg Vorbis. It can compress down to a smaller size than MP3 while still sounding good. Best of all, it is designed to be completely free of patents and does not require the use of proprietary software.