Sounds like you are running ferrous tones if both numbers are low numbers. Ferrous tones will give high tones on all low ferrous numbers, so the conductivity numbers can be high or low and still give a high tone as long as the ferrous numbers are low.
Now if you are running conductivity numbers as long as the conductivity numbers are high the tones will be high even if the ferrous is high or low.
I like the ferrous tones myself as I hunt a lot of areas with nails, this way nails may read high conductivity like a coin will, but if the ferrous is high they will be low tones to let me know it is a nail. Now where I get a high tone like a coin in ferrous is the rusty crown caps and some tin cans as the conductivity will be low and the ferrous too will be low, but very easy to tell as the cross hairs or the conductivity number will be low.
Here is a example if ferrous tones.
F# C # Tone
0 0 high Crown cap
31 0 low trash
0 30 high silver quarter
31 31 low nail
Now if you are running conductivity tones this is what you will have
F # C# Tones
0 0 low
31 0 low
0 30 high
31 31 high
As you notice when you get a low ferrous number you have high tones in ferrous tones no mater where the conductivity number are. Now if you run conductivity tones the higher the conductivity numbers are the higher the tones is no matter what the ferrous numbers are. This is why I feel you are using Ferrous tones is why you have a high pitched when both the ferrous and the conductivity number are low.