Wanting To Set A Text That's Still In Copyright

wat do?

I have no idea about the prospects for performance/ publication atm. 

I don't have a huge amount of money to spend (let's say double digits, max)

Look up who has the copyright and ask for permission, from their yall can work out the details about what you can do with the poem. If its a publishing house that owns it they may have rules and what not about what you can do. 

I know that was the case when I set E. E. Cumming's poems. They have a very convenient section on the website that owns the copyright to his poems that deals with this stuff. Other people and companies might have something similar. 

ask for permission

I kinda wanna know the general parameters before i do that. I don't even know if I'll complete the composition, let alone release it or more. Actually making money from it seems like a *very* remote possibility. From a practical/ realistic standpoint, I wanna know if I should even care,

Its a win-win situation: either they never hear anything about it because it isn't successful enough, or it is successful and then I'd worry about copyright!

I kinda wanna know the general parameters before i do that. I don't even know if I'll complete the composition, let alone release it or more. Actually making money from it seems like a *very* remote possibility. From a practical/ realistic standpoint, I wanna know if I should even care,

thats the thing, each copyright holder will be different.

Some only want to make money and will not give their permission unless its profitable. Others just want to be recognized and will gladly give you permission. Others just want to keep track of who is using their stuff and how. Some people have very specific guidelines when it comes to how you use them. For Example: when I got the e.e. cummings poems they ask that I did not alter the original text or omit text. And in some cases, permission is completely off the table. That is the case for Robert Frost poems. His estate decided that they would not grant permissions to anyone anymore for use of his poems. 

Be for permission, you start the dialog and negotiations that are required to set the perimeters. 

Here are some publsiher's permission page, you can get an idea of what you have to ask with some of them:

http://books.wwnorton.com/books/permissionhelp.aspx?id=4672&mid=66

http://www.oup.com/us/corporate/permissions/?view=usa

http://www.cambridge.org/about-us/rights-permissions/

Set it, and then file it away. Eventually, long after you're dead, it will be in public domain and people will be able to play it. You don't need permission to write it, you just temporarily need permission to use it.