Twenty years ago I was in a Men's therapy group where, by happenstance, three of six guys were closet crossdressers (including me). One guy had not told his wife of 15 years and said he would never tell her because he felt it would hurt her and her feelings about him. He absolutely adored his wife and did not wish to hurt her or their relationship in any way. I hope he was able maintain that stance as I'd hate to think his wife ended up feeling betrayed by him as I know was not the case.
That said, I think those who say a willful omission is not a lie are playing semantic games.
Many years ago I was stockbroker. When selling, under corporate pressure, a product that I was less than thrilled with, I often thought that the most important thing in the sale wasn't what I said but what I didn't say. Why? Because what I knew but didn't say would have killed the sale. Is this comparable to holding back on telling about your CDing? Maybe not exactly, but this is an essential piece of yourself which I think you owe the person you are marrying - it's too big a deal to hold back.
