Add custom thread field to thread's subject

[ZiNgA BuRgA]

If you want to hard code the field into the subject, that^ could work, but the problem is that you're relying on the client supplying you the right information (may be okay for your purposes).
XThreads supports doing the reverse, ie bringing the subject into a thread field, but otherwise doesn't really touch MyBB's subject line.  So for what you want, you'll probably need a code edit.

Open newthread.php, and before

PHP Code:

if($mybb->input['action'] == "do_newthread" && $mybb->request_method == "post")

---

add

PHP Code:

if(in_array($fid, array(1,2,3))) $mybb->input['subject'] = "{$mybb->input['xthreads_singer']} - {$mybb->input['xthreads_songname']}";

---

(replacing 1,2,3 with the list of applicable forum IDs)

Untested code.