I try to stretch my synthesizers in order to get the most out of them. Since I've long been searching for a professional analog monophonic synthesizer and still haven't found the right one, I’ve experimented quite a bit with the Prophet ’08's monophonic side. For one, the P’08 offers the ideal keyboard size - a full five octaves. There's no need to hit an octave button when you run out of keys, as you constantly need to do to transpose a melody beyond the range of the typical three or three-and-a-half octave keyboard. You'll simply never run out of room on the P’08 keyboard, so that problem is solved once and for all. In addition, the "Split Mode" essentially allows you to have two independent mono synths ready to play, without having to switch between keyboards or hit program buttons to change sounds. This is a tremendous advantage over the usual one-sound-per-instrument arrangement.
The biggest problem in using the Prophet ’08 as a monophonic synthesizer is due to an actual flaw in the instrument: in the unison mode, it makes a nasty "click" sound in between notes when played in a legato style. This is especially true when using pulse width modulation. Recent operating system updates have improved this problem, but it still requires a bit of finessing in order to entirely hide it.
This problem annoyed me for a while, so that I had given up on the Prophet 08's monophonic abilities. But I've finally figured out a way around it. Nothing brilliant here, I realize, but I thought I'd mention it for others who may not have entirely resolved the problem or who are using an older OS.
First, when using "Unison Mode," select only the "1 Voice" setting; avoid the "All Voices" settings if you can. Second, when using pulse width modulation, leave the "Key Sync" button off, so that the pulse width isn't retriggered every time you strike a note. These two techniques alone eliminate much of the clicking problem. If you want to improve the sound even more, then add an amount of glide, extend the attack time, and shorten the release time. These last two settings will avoid notes from running into each other.
The final touch that will put a once-and-for-all stop to the clicking sound is only possible when the music allows for it: a detached playing technique. Certain patches require this anyway, such as when you want to articulate notes somewhat like a violinist. A slower attack and a complete cessation of sound before the next note strike will entirely resolve the problem. A generous amount of reverb will smoothen out the musical line and keep the melody from sounding overly detached.
I've found the monophonic sound produced by this setting to be perfectly satisfactory, allowing the Prophet ’08 to double as an excellent monophonic synthesizer.