Rufus Wainwright—pictured to the right of musical collaborator Antony Hegarty—plays solo with piano at Benaroya Hall Sunday, Nov 8th.

When interviewing the God-gifted vocalist and piano-man, I ran out of time before asking Wainwright, "Why don't you lend your vocals to a whole album of dance music?"

Understanding the tragedy of not asking this question and how I could have reasonably asked it in the first place requires some background.

Wainwright's got one notable dance track, the 2007 remix of his song "Tiergarten." German team Supermayer turned the sashaying, music-box tune into 13 minutes of rainy-day minimal house music.

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The "Tiergarten" remix was a triumph, but easy enough to accept as an isolated experiment. In 2007, Wainwright was making evermore orchestral pop and covering Judy Garland at Carnegie Hall.

Then Wainwright's billowy-voiced buddy Hegarty dropped an unexpected disco masterpiece, and now I'll always want Wainwright to do the same.

Once upon a time, nobody associated either artist with dance music. They were just great singers who played piano and sometimes sang together (see Antony and the Johnsons' "What Can I Do?").

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But Hegarty's unexpected involvement with the group Hercules and Love Affair made a big splash in 2008, resulting in a self-titled album that was one of the year's best, and an arty, catwalk-ready lead single ("Blind") that ended up a club hit.

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As Hegarty moved from theater to nightclub in 2008, Wainwright moved from theater to opera house, composing an opera called "Prima Donna" which was put on in Manchester July of 2009.

But in the middle of writing his opera, didn't Wainwright listen to Hercules and Love Affair? (Of course he did.)

Didn't he love it? (How could he not?)

Didn't it make him recall the "Tiergarten" remix and think to himself, "Hm, maybe I should've pursued that sound"?