The noble and cleric can't read? Classes that effectively have to read in 5e and similar systems:
Bard: plays, music, stories
Cleric: holy texts
Monk: holy texts if they are the monastery type of monks
Paladin: if trained w/clerics or in a temple. not if they are wild-sprouted paladins.
Rogue: thieves' cant, smugglers for manifests, forgery. really just the average cutpurse and enforcer wouldn't need to
Wizard: a nerd's nerd
Many musicians have famously come from poor illiterate backgrounds, being able to play a tune, sing, or recite a story doesn’t require reading skills. It requires good memory to recall what youve heard or creativity to make up something new. So i an totally get behind a bard that cant read.
Homer may not even have existed, let alone been blind. And if he did exist, may not have written both the Iliad and the Odyssey. And if he did write them, very well may not have written them from scratch (but was instead just the person responsible for writing down what became the definitive version of a more widespread oral tradition). So he's perhaps not the best example to use. (The notion that he's blind is based on the assumption that a certain bardic character in his writing was a self-insert.)
A "bard" isn't just any musician. They're a highly educated experienced user of language. Telling stories, composing poems & songs, and being in the employ of a noble to do so. In popular culture there's also often the implication that they use these skills and that access to be involved in espionage in some way.
I think Robert Jordan's Wheel of Time series does an especially good job of this. It has gleemen, which are reasonably well-trained in music, storytelling, and other performing arts. Gleemen travel around from town to town making their living playing at taverns and the like. Then a step up from gleemen it has bards, which are more well trained and who perform explicitly for nobles. In either case you can expect a great level of artistic skill, but I'd be shocked to hear of an illiterate bard, but maybe only mildly surprised to hear about an illiterate gleeman.
