Believer was (in?)famous for being a Christian death metal band in the early 90s when death metal itself was still fairly novel, and Christian death metal unheard of. Whatever else I might have thought of them, I've always thought that Believer was one of the most original and talented early death metal acts out there. I wish more Pennsylvania boys would have had the cajones and drive to get out there and create something new and technical like they did. In 1991 it was much braver to include non-conventional, genre-defying content on death metal records. It's a very mature style now, but two decades ago the genre was still forming its identity and deciding on the rules, and as such, style solidarity was valued, and dissent was not well-tolerated. Since Believer was Christian maybe they reasoned they were an outgroup anyway so who cares.
In any event they put this composition in their title track; in all honesty, most of the time extra-genre inclusions on metal albums are low-quality filler, worth more as signaling than real content (i.e., "Look! We're talented because we can compose in in this other respected format. Now you must acknowledge that we're legitimate and metal is legitimate!" The same thing happens in other genres too. Was Body Count really a good metal album, or was it just novel for Ice-T to show that he could do metal too?)
Believer didn't stop with the classical part. There's a reggae bit pasted into a song that sounds more like Suicidal Tendencies-style hardcore ("Stress"; listen here) and a screwy but intense lead-in to Not Even One.
*I have Quarteto da Pinga and IR8 too. Yes I'll be posting them. And I had to go to Singapore to get them (yes, really) back before you could download things. The internet ruined tape trading conventions.