I wrote this for a synth project where I only used FM4 for all synth sounds. The project was more about learning some basic FM synthesis more than anything. The "guitar solo" is also FM4 played through some distortion.
Before buying this synth (FM4), FM synthesis was a complete mystery to me. I had tried a couple of FM synths before but they always left me very confused. FM4 was the first one I actually thought was somewhat intuitive to work with.