I ALWAYS forget this so I am posting it for myself and anyone else who stumbles upon it.

function subval_sort($a,$subkey) {
 foreach($a as $k=>$v) {
 $b[$k] = strtolower($v[$subkey]);
 }
 asort($b);
 foreach($b as $key=>$val) {
 $c[] = $a[$key];
 }
 return $c;
}
$songs = subval_sort($songs,'artist'); 
print_r($songs);
Array
(
 [0] => Array
 (
 [artist] => Fleetwood Mac
 [song] => Second-hand News
 )

 [1] => Array
 (
 [artist] => The Decemberists
 [song] => The Island
 )

 [2] => Array
 (
 [artist] => The Smashing Pumpkins
 [song] => Cherub Rock
 )

)

Taken from this site:
http://www.firsttube.com/read/sorting-a-multi-dimensional-array-with-php/

Thanks!