Change default button name

The default button name is “Purchase”. Where can I change that? I’d like all buttons to default to “Buy MP3”. I know I can specify text for each button as I place it in a page, but I’d rather just change the default. Thanks.

EDD is the perfect solution to my needs, btw. GREAT plugin!!!

http://ww.wp.xz.cn/extend/plugins/easy-digital-downloads/