In Tartarus:

Perseus wanted to lighten the mood as the group trudged through the pit. The problem was he couldn't seem to think of a way to do that. He looks around and the redish tint was still there, like a soft fire glow, he thought. Suddenly a song came to mind one all of them should know. Annabeth noticed Percy's expressions and became suspicious. 'Percy, what are you going to do?'. He just grinned and sang:

From here all the world is a raging fire
I know You can see what I see
Well they'll have their way
Everyone breaking down
If we turn and we flee

All I know is I'd rather die than believe a lie (Live a lie)
I cannot follow the blind

'Come on Annie you know how I goes." Annabeth just smiled and sang with him:

We'll never back down
We will not relent
Now or never, till the day that we dreamed of
I see it coming
As we press on
We will not relent
Now or never, till the day that we dreamed of
I see it coming to life

Percy:
These voices are making me lose my mind
I know You can hear what I hear
Well they'll have their way
Everyone's heart bled dry
If we turn and we flee

Annabeth:
All I know is I'd rather die than believe a lie (Live a lie)
I cannot follow the blind

This time Bob and small Bob hummed to the tune:

Together:
We'll never back down
We will not relent
Now or never, till the day that we dreamed of
I see it coming
As we press on
We will not relent
Now or never, till the day that we dreamed of
I see it coming to life

Annabeth:
When darkness arrives
I cower and hide
But You found a way to pull me out
They come in the night
To take what is rightfully in the hands of every son and daughter

Percy:
We'll never back down
We will not relent
Now or never, till the day that we dreamed of
I see it coming
As we press on
We will not relent
Now or never, till the day that we dreamed of
I see it coming to life

The foursome continued their journey and occasionally burst out into song courtesy of Percy. The songs seemed to lessen the burden of the journey for the most part. Music is food for the soul. Whoever said that was at least partially correct as it seemed music wormed their way into their hearts.