Technically speaking, only a little over half the album was written for Jon, since the whole thing was supposed to be split between Jon and Zak. The songs that made it to the final album were basically the songs that Jon felt still sounded good with just his voice. Consequently, one or two songs (including the title track) were cut, and "Stay With Me Awhile" was added at the last minute. (Almost literally; a mere month before the album was released, the official track-listing contained only 10 tracks, before "Stay With Me Awhile" was added.) The song "The Nonsensical Ravings of a Lunatic Mind" from the first JOP record was actually one of the lost tracks from P&M, possibly the title track, presumably drastically re-written. Even a lot of the songs to make the album proper were allegedly rearranged for Jon's voice. To what extent, though, I'm not sure, although I believe "Morphine Child", "The Rumor", and "Back to a Reason" were supposed to be, primarily Zak songs, while some of the other tracks, like "Drive", were supposed to have dual lead vocals.
I have mixed feelings about the whole thing. On the one hand, Jon does sing the whole record very well, and I do greatly enjoy the final track-list. I cannot imagine the record without "Stay With Me Awhile". On the other hand though, I would be very interested to have heard those lost tracks, and based on the live performances that were done with Damon Jiniya, many of those songs would have sounded very good with split vocals. At the very least, I wish they had at least recorded some of Zak's vocal parts, since they ended up using dual vocals on the tour anyways. And I do think that moving forward with the album without Zak was a huge mistake, although my reasons for that have less to do with quality of the record itself and more to do with how I feel Zak's departure and a new round of line-up changes might have lead to Jon's disillusionment with Savatage. But I will go into that in a few months in the Discography thread...