create new background..example-red
Make 2 stroke paths with pen tools
-1 is white -1 is yellow
Go to Object > Blend > Blend Options, enter Specified Steps = 20.
Then with the 2 strokes selected, go to Object > Blend > Make.
This will blend 2 white strokes and create an abstract wave effect. If you want to change the Blend step, you can go to Object > Blend > Blend Options or double click the Blend Tool(B) on the tool bar.
here’s the result..:-)