If you Google for “most used audio file formats”, you see that both aac (Apple's Advanced Audio Coding) and flac ( Free Lossless Audio Codec) are very popular, but both file types are missing in the standard jAlbum filetypes.xml file.

So my request is to add these types to the standard jAlbum filetypes.xml file, so that users are not forceed to change or make there own filetypes.xml file.

The file types ram, rm and weba are in filetypes.xml file, but they are not mentioned in the surveys, so may be they can be removed.

Well on my Windows 10 PC an aac file is supported by Firefox, as you can test with the last thumbnail in my audio tracks test album.
I did not check that on mobile devices, but Firefox is hardly used on mobile devices.
The aac type apparently comes from Apple, soI think it is an excellent choice for audio files in albums.

Converting an aac file to mp3 is not a good idea, because the quality of aac is better then mp3, see here.

Firefox on my iPad supports too aac.

Yes it says:

Advanced Audio Coding format, designed to be the successor format to MP3, with generally better sound quality.

There's simply no reason to use anything other than MP3. Sure, some other format might have "better sound quality," but who's listening to the sound clips in your album on a nine-speaker surround sound system with Dolby Atmos speakers firing at the ceiling for the sound effects? If no one can tell the difference in a double-blind test, it doesn't matter. They're listening on ear buds, or, like me, with some truly ancient Altec Lansing computer speakers. Not exactly Decca ffrr!

And just because something was developed by Apple doesn't mean that it's a good choice for inclusion in an album. Apple generally doesn't do "open source" for much of anything. Ninety percent of your visitors are not on Macs.

Well aac is better as filetypes rm, rma and wma which are useless.

Adding aac to this file does not mean that you have to use it, it is the user who decides to use this format yes or no, but he should get the opportunity to use it without editting a filetypes.xml file.

I really don't understand why you guys are making so much noise about a simple proposition to add 2 lines of code to a file!

It's because, as usual, you haven't done your homework. You're too lazy to do the checking, and just expect others to do it for you. "This works for me, so it should be added. I've never heard of these other ones, so they should be removed." It's all about you. It's always the same story with you, and we're really, really, really tired of it.

Unlike you, I've done the research. You're asking for the addition of a file type that doesn't have universal browser support. That's the wrong thing to do.

... so I don't care about anyone else's system."

It's not all about you.

How have you arrived at that conclusion? I default to Firefox on my PC, my Macbook, and my Android phone, and I stick to that so that things like bookmarks stay synchronized across all of them. And guess what about AAC on Firefox on Android - it doesn't work.

But once again, because André doesn't use Firefox on Android, he assumes that no one else does, so it can be ignored.

It's not all about you.