LDR circuit does not change sound frequency
There's no such thing as a generic LDR. They're available in a wide range of resistances. This one varies from 30k\$\Omega\$ to 5M\$\Omega\$, while this one varies between 11k\$\Omega\$ and 150k\$\Omega\$. They will give you a completely different output range, which the software may or not may detect properly.  

The first one will give a voltage between 3mV and 0.5V. If you have an LDR like this the output voltage may be too low.
The second one, on the other hand, will give you a voltage between 0.1V and 1.15V, which is already a bit better. A 4.7k\$\Omega\$ resistor will raise this to 1.5V.