Personally, I believe the various tones to be a waste of time, just a distraction.
I have dug many signals that sounded like absolute crap, only to find that it was a low carat ring.
Conversely, I have dug real sweet, high tones to find not the silver I was expecting but a high carat ring.
Crucifixes, chains, big pendants, small pendants, deep, shallow, lying flat, on edge, low carat, high carat, combination silver and gold, on it own, next to ferrous etc etc. The variables are endless. And each of these all sounds a little, or a lot different.
Forget trying to work out if the signal your hearing is gold or not. Most of the time you will be wrong anyway.
Some people say that you should dig everything, including nulled signals. I don't do this, might as well have got a PI and dig every signal.
Having said that, at a lot of locations I hunt in PP (all metal) and do dig every signal, for ferrous objects are few and far between.
But there are also a few very good spots that I work that are loaded with heaps of ferrous. Some quite large, these I dig up and drag away just to stop them from blocking out large areas of ground, smaller pieces I pile up in selected spots, leaving absolutely hundreds of small coinish sized bits of rusty metal everywhere that I have to hunt over.
The point I'm making is that in amongst all this crap, with the machine making all sorts of weird and wonderful sounds, it desperately trying to null on the ferrous rusty bits while at the same time trying to sound off on the many coins, bits of brass, copper, lead and also jewelry in the area, the only way to work is to dig ANY repeatable sound, however broken or scratchy or crappy it might sound. And even though I've been hunting for nearly 4 years and have found 300 odd pieces, every time I do I'm surprised.
Pain in the arse hunting this way? Your absolutely right! But I bet I find a lot more gold than most. Maybe not as much as some of our friends in France but I find gold nearly every hunt and I hunt often.
By all means, listen to the advise of the learned folk on theses pages but do yourself a favour and don't stress too much about the tones.
If it sounds off, regardless of how good or bad, high tone, low tone... whatever.
Just dig it!
Lou.