Adding Songs to Music/iTunes on iPhone

Hi -

A while back I asked this question but, because I phrased it badly, did not receive an answer that resolved the issue one way or the other. So I'll try again...

My son has an iPhone and iPad, but no computer. I emailed him some music files of songs his band recorded some years ago, and he was able to hear them by clicking on the individual email attachments. But our question is this: Is there a way to get those files into the iTunes library on his iPhone (along with all the other music he's purchased from the iTunes Store)? If they were in that library, he'd be able to use bluetooth to stream his old recordings to bluetooth speakers at home, and to use CarPlay in his car to hear them.

If he had a computer, he could import the songs to the iTunes Library on that computer, then sync his iPhone's iTune Library to the computer's. But without a computer, Is it possible to get the result he's looking for?

Thanks in advance for any help anyone can provide,

Shelly