Due to the release of the Collection of SaGa - Final Fantasy Legend, I can't host any music files here. Rather, I can provide you with links to official services and other sites.
Final Fantasy Legend OST
Fortunately, Square Enix has made it easy for us to listen to the soundtrack. It's available on every popular music streaming platform.
Album Covers
Below is the official Japanese album cover and one based on the NA title screen.
Fan Music
The best place to listen to Final Fantasy Legend fan music is on YouTube.
Extracted Game Music
The fan base has gone a long way with emulation. In the early 2000s, they came up with 'extracted game music' (a.k.a. chiptunes). They extracted the programming of the music from every classic video game and built digital soundtracks with them. With special music players, you can play these music files as if they were MP3s. And they're far better quality than MP3 because it's the actual programming of the song that you're listening to! In this realm, classic Game Boy music is under the 'GBS' file format. Music players that support GBS can be found on any device: Windows, Android, iOS, Mac, and Linux.
My favorite feature about this music is how small it is. Final Fantasy Legend's GBS soundtrack is around 300 KB while an MP3 soundtrack is around 400 MB! So you could quite literally have hundreds of classic gaming soundtracks on your iPhone or Android phone, and barely make a dent in your phone's storage.
If you want to learn more, read my tutorial for Extracted Game Music. My tutorial also provides links where you can download GBS music. Extracted game music can be converted to MP3, too. My tutorial provides directions on that process.
Midi Music
MIDI music is a relic from the early days of the Internet when it was the only music we could download with our slow dial-up connections. It's fan music because MIDI files are made by people playing the songs on electric keyboards. The #1 website for video game MIDI music still exists today: VGMusic.com. There you can download Final Fantasy Legend's entire soundtrack in MIDI format.