Recently I received a 1929 Scottish Psalter: Metrical Version and Scripture Paraphrases, With Tunes through Abebooks. It was shipped from a bookseller in Scotland. It's the split-leaf version. The Psalter part is split-leaf. On the bottom of the "dutch door" you'll find the words for all 150 Psalms. The top of the "dutch door" has the melodies. Most Scottish Psalms can be sung to many different melodies. The minister will call for the singing of a Psalm to a specific melody. The worshippers will then flip the "dutch doors" to get to the right Psalm and the right melody. Another interesting feature is that the music is not set in notes but in do-re-mi, etc., fashion.