^^Im pretty sure that Jon's voice is pretty severely damaged now, for whatever reason- overstrain in the early years or smoking in the 90s..... I don't know...

You can tell he is very very careful with his voice now, whereas in the early 90s he could just let himself go and try different things and scream etc

He is still able to sing well on many songs using good technique though; clearly he has learned a bit in the last few years about how to make the best of what he has. But sadly he no longer has a pleasant sounding tone, it's extremely thin and nasal, plus the way he delivers the lyrics is slurred.