x(t) = a*sin(w1t + deltaphi*sin(w2t))
With the "source block" it is not possible, you can just set a fixed frequency.
This is phase modulation of a carrier. You can implement it by multiplying (multiply block) the carrier (signal source) with the output of a phase modulator fed by the modulation signal which in this case is a sinusoid.
Example flow graph in GRC (numbers not particularly sensible, just demonstrating it works):
Notes:
- Your "deltaphi" parameter can be put into either the Amplitude of the signal source or the Sensitivity of the phase modulator; it's equivalent.
- For maximum computational efficiency, replace the carrier source and Multiply block with a Rotator block. However, it requires the frequency to be expressed in radians per sample and so is not as convenient for casual use.
- The output is complex (analytic). If you want real output, just use a complex to float block after the multiplication.