Since you are using cpld then you don't have memory blocks to store any tables.
The easiest way is to store one small cycle sinusoid on wires(e.g. as HDL constants) then run a clock to read the cycle out continuously.
You can use several ways to change the tone e.g. different clocks or better different clock enable rate or jump the values using same clock.
The equation for frequency would be this:
f = clk frequency/number of data per cycle.
An example 64 data cycle can be produced as follows:
data = sin(2*pi*(0:63)/64)
you will need to scale up the data to integers in hardware.
Then sing the tone out...use audio range for your frequency so that human can enjoy the songs
