Why is his singing heard on a "distant hill"?

The
answer in this case, as it is with most poems, really depends on the way you choose to interpret
it. That's not to say that every interpretation has a sound basis in the work itself, but the
symbols of 's "" don't offer an easy, singular answer. I'd offer you a few ideas and
musings on what it could mean.

For one, as you read the poem you might notice
that the free bird never sings. It "leaps" and "floats" and thinks of food,
but it does not sing. Every reader is welcome to disagree, but personally I don't think it's
accidental on the author's part. So why does the free bird not sing? It's possible he doesn't
need to. Maybe he doesn't want to, or perhaps he's forgotten how to. In contrast, the caged bird
does sing. That's pretty much all he can do, because:

his wings are clipped and his feet are
tied

So why is the caged bird's song heard on
"a distant hill?" It's very likely that it has to do with desperation and passion. The
song is everything the caged bird has; freedom is all he thinks about. The "bars of
rage" stand between him and everything the free bird experiences. The caged bird doesn't
even know what he is missing, because he sings:

of things unknown

but longed for
still

We can imagine that kind of longing
gives the song the power to be heard far away on the distant hill. Now this could mean that the
song itself is powerful, but it could also mean that the message itself is. After all, Angelou
says that the song is heard:

for the caged bird

sings of freedom

So we could interpret that as saying it's heard because
he sings of freedom. It's possible the message is that freedom songs carry further
than others. After all, most of us are free, but we can imagine being trapped and wouldn't wish
that fate on others. The free bird isn't just symbolic of being freehe's also symbolic of being
a bird. He does the things a bird is supposed to do, while the caged bird is trapped in an
unnatural state. Therefore you could say that the caged bird's song is heard, since we care to
hear to hear it.