When Sade's first concert in a decade was announced last fall, she was billed as the sole headliner. Interest was expected to be high because the British R&B singer hadn't toured in years.
But a couple of weeks after tickets had gone on sale for her show in Baltimore, which takes place Thursday, promoters decided to add some top-shelf support: Grammy-winning pianist and singer John Legend.
It turns out one headliner doesn't cut it anymore.
Reeling from last year's concert season that saw ticket sales fall for the first time in 15 years, artists and concert...