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!