How to use math.random w/ in pairs?

The pairs function returns all the keys and values of the argument table, math.random returns a random integer. For this reason, you can't directly index a value at a non-integer key with a value generated from math.random. Here's a potential workaround:

function obtainRandomKeyValuePair(tab)
	local randIndex = math.random(1, #tab);
	local curIndex = 1;

	for k, v in pairs(songs) do
		if curIndex >= randIndex then
			return k, v;
		end

		curIndex = curIndex + 1;
	end
end

You would then call the function with:

local key, val = obtainRandomKeyValuePair(songs);

EDIT: Apparently the length operator doesn't work on tables with non-numeric indices. That's really poor design. At any rate, I would switch to a 2D table. Here's an example:

local songs = {
	titles = {
		"Friday",
		"The Song of the Cebu",
		"Problem",
		"Bills"
	},
	ids = {
		"268763467",
		"142570249",
		"261244793",
		"165508381"
	}
};

local randIndex = math.random(1, #songs.titles);
local title = songs.titles[randIndex];
local id = songs.ids[randIndex];