Scribus is great. It's a FREE professional level typesetting system. They say there's a few bugs, but I haven't seen them yet, and I use it multiple times a week. Just save frequently, don't chain too many text boxes together, and you'll be fine.

There's a little bit more of a learning curve, but if you are fairly techey (like me), you shouldn't have too much trouble. Just keep playing with it, it'll pay off in the long run (it's what I used for my book on the universal prayer, see sample). Combined with the meinrad fonts (see below), you can do awesome things with scribus. I did a 70 page book recently with it (here's a sample)). It's amazing.

You can make wonderful aids like this or this, which I eventually downsize, and print on a single folded 8.5 x 11.

http://www.scribus.net/canvas/Scribus

Let's see, with 1/2 inch left and right margins and 1/2 inch gutters between columns, you'll have !5"/3 = 5" column width that everything will have to fit into for each column. You should be able to keep 1/2 inch to 3/4 inch top and bottom margins, for a column text height of 9.5 to 10 inches. This is actually a tiny bit more generous column width than one would have with 8.5 x 11 bifold, but only a tiny bit, so don't get all excited that you'll have lots of room. You'll doubtless find yourself having to shrink hymn inserts, probably by different amounts from different sources.

I don't know what software would work best for this, but i have used Word and/or LibreOffice, as well as Finale (for direct music engraving of hymns to the right size).

While I'm sure you find yourself embedded into the 11 x 17 tabloid size, trifold format, my own preference is for 8.5 x 14 legal size, bifold   the 7 x 8.5 inch result has a comfortable feel to it and there is a little more than 6 inches of column width, which makes formatting much easier.

Others will have their own suggestions, and with all of them, YMMV. Good luck!