I have a 3 h.p. cabinet saw by Rockwell/Delta, vintage 1960.    It is solid and has served me well.     Yesterday I did two wide crosscuts, trimming the tops off some cabinet doors.   On the second cut, there was a new bass note to the sound of the saw.  The higher pitch was still there, but a new lower note was there in harmony.  We all know the sounds of our various machines, and this told me something had changed.
A friend recommended I check the tension on the belts (this saw has 3).    That involves pulling the top off, which I can do, but before doing so I thought I would solicit opinions on this forum, just in case any of you have had a similar experience.
Thanks in advance.