How can I optimise and improve this circuit for audio applications?
Looking at the sine wave, there is no DC element. So using C1 polarity cap will distort the signal, you can use non-polarity aluminum cap. 

C1 R3 is a high pass filter, 100 ohm is too low too drive properly for line output. Recommend value is 10uF and 10k ohm, the roll off frequency is 2Hz and below.

Increase R1 + R2 resistance to above 10k ohm, opamp would drive better.

The circuit gain is 5, you would get 2.5V instead of 2V.

Use a low noise opamp like MC33078.

Add a low pass filter by adding a small cap across R1.