Question with FM Modulator

Hi all,

I'm using an oscillator to modulate my audio signal into FM signal. I've done some simulation using ADS to sweep the input voltage (audio signal) across the frequency.

Here's some image to draw the picture more clearly. My audio works around 100mV, referring to the slope of voltage versus frequency, is this oscillator sufficient to modulate the audio signal? Or do I need to increase the slope? If i do, what should i change in the schematics?

Is this an issue about modulating index of the FM modulator?

Thanks in advance