A bit out of date surely? Vinyl has long been replaced by CDs, and even these are rapidly being replaced by MP3 files from Itunes, etc.
It's possible that disco might also mean CDs or DVDs. In any case, Duolingo is still talking about letters too.
HD (just the names of the letters: agá- de. Sometimes called only "disco", that's ok too :)
Wouldn't album also be a correct answer? It works in Spanish at least
If this is vinyl why is LP accepted? And if this can also refer to cds, why is CD accepted??
Duo translated disco as "album" earlier. Now that translation is marked wrong.