I love this question! I have a couple favourites.
"I.G.Y" by Donald Fagen. It's about International Geophysical Year. The lyrics have techno-utopian visions:
"On that train all graphite and glitter / Undersea by rail / Ninety minutes from New York to Paris"
"Here at home we'll play in the city / Powered by the sun"
...even AI alignment (and anti-aging?):
"A just machine to make big decisions / Programmed by fellows with compassion and vision / We'll be clean when their work is done / We'll be eternally free yes and eternally young"
And I just find the chorus so uplifting and inspiring:
"What a beautiful world this will be / What a glorious time to be free"
"Well Rested" by Kero Kero Bonito. This has more of an environmentalist / "Mother Earth" theme. But it also has a more general longtermist theme of perserverence and ensuring civilisation is "well rested" (which I interpret as being wise and resilient). The final lines are especially powerful to me:
"We have survived a hundred apocalypses / Doomsday hasn't come yet / You cannot stop civilisation"
It's also just an epic song that gets me up dancing!
I find Where The Hell is Matt? 2008 to be the most beautiful video I've ever seen. For years straight it always brings joyful tears of love and compassion to my eyes. The mesmerizing song and the shots of people from all around the world dancing without any bigger purpose but to celebrate life itself remind me of the immense value that happiness has.