I think the difference would be in how much server space each requires. Text and images take up a lot, but still relatively little compared to audio, which is dwarfed by video at the scale that this would take. It's an interesting idea, but someone always has to pay somewhere. Maybe something like integrating Mopidy into Mastodon/GnuSocial might work and could then piggyback off the already created software, but I'd think it would be closer to a reddit clone than a twitter clone.