One approach would be to use InDesign's Paragraph Shading feature (in the list of each Paragraph Style's menu), but I don't think transparency is supported, only tint levels.

I don't believe there is any solution in which such shading could be integral to the text; ID has no features that allow assigning transparency to only one part of an element. (That is, if the text is 100% solid, any background, under/overlining, border etc. must also be completely solid.)

If it's for a magazine cover where some manual composition is both expected and a reasonable way to achieve the layout, simply using a shape around the text, such as a series of rectangles of defined height, and assigning them or their layer the desired opacity would be the first approach I can think of. There are other ways to combine text and shapes and levels of opacity, but all are variations on that.