You only have to memorize One tone.
. this will give a constant tone without interruption at a particular frequency (remember Zero Sink is actually Lift , as your no longer loosing height)
A Lower constant tone than Zero Sink means your loosing height.
A higher "interrupted tone" indicates Lift and height gain.
the faster it's interrupted the Higher the Lift.
It seems complicated at first but a little practice
and it will be second nature
That's the basics, however things are never quite that simple ....
With a Glider, Height can be converted to Speed, and Speed can be converted to Height
Elevator stick input will vary airspeed and give False Vario readings
e.g. Down Elevator increases Speed & Sink rate
so the Vario will respond appropriately with a Sink indication.
On the other hand Up Elevator on a Fast flying Glider kept above Stall speed
and the Vario will indicate Lift as the Glider converts Speed to Height.
On a simple Vario this is normal and the Pilot learns quickly
the effects of Stick inputs on Vario response.
A more sophisticated Vario also reads the Airspeed
and compensates Vario output as airspeed is varied
this is know as a Total Energy Vario. or T.E. Vario.
that I'll leave to someone else to explain,as I feel it best to learn to use a normal Vario first
before getting involved in the TE systems.