A little bit of background...
When the Praise Song Advisory Team, the group that selected the songs for inclusion in Sing! Prayer and Praise, were discussing the elements of the book, it was decided to have only two indices: one for titles and the other for arrangers, composers, and lyricists. The hope was that those who used the book would contribute their thoughts to which songs best fit for selected scriptures (lectionary), themes, times in worship, and so on. This didn't work as hoped, though users of the song book seem more eager to contribute now that they've had more experience with the songs. So, we're trying a new approach!
Indexes are now available online, however. The lectionary index will be a continuing project and has been completed to July 2013. You can submit a song suggestion for one of the indices including suggesting a specific scripture for a song here. You can also suggestion new topics/themes, add to the seasons of the church year, and suggest new worship elements at the same link.
(Many thanks to Douglas Fauth for his significant contributions to the indexes!)