Magic Music Visuals

Hi,
I am trying to show/hide - via the transparency fx - a starfield effect. MY GOAL: Have it "on" 30% of the time and off about 70% of the time. In other words, about 70% of the time the transparency amount value is 0; and then then about 30% of the time, the transparency amount is > 0 or closer to 1.

I am trying to figure what match functions, when operated against the Playback Time (or any other variable for that matter).... would produce such a result. I have tried the sin(x) and others but no luck.

Any expert recommendations to get a expression output of 0 about 70% of the Playback Time and a value > 0 or maybe even > 0.3 around 30% of the time?? It could take me and my math skills years to figure it out

Thanks In Advance!!

Your question is a bit ambiguous. Are you asking to have something visible for 70% of the audio track, or are you asking to have something appear and disappear at regular intervals in the ratio 70:30 (as suggested by your mention of sin(x))?
There's no maths required for the former - except for the %age of the track you want. No maths required for the latter either:

THANK YOU!!! so much for your help.

Yes... my request was ambiguous (70% contiguous of the entire time, or on/off for 70%) - it was on/off.

I saw your kind examples; they worked and taught me something new about MMV

Thanks Again!!