What the H#!! is this noise? Slant six mystery engine sound...

so, what was the cause of the noise??
i ask b/c i think i heard the same one tonight on the way home..70 Valiant 225, sounded loudest right at front of valve cover/alternator area...my fan belt was super tight, and was a little gummed up in the alternator pulley area...smoke and everything..
been a while since i have done anything to anything in there, so could be anything :help:
Blind