When a pop singer who has long faded from the limelight suddenly starts appearing in your Twitter timeline in the form of glowing, nostalgic re-evaluations, they're either gearing up for a comeback . . . or dead.

In the case of 28-year-old singer Aya Matsuura, the reason for the brief flurry of critical reappraisal was the happy news that she is about to give birth to her first child. Still it got me thinking about the trail she blazed through the J-pop scene as a teenager, what it shows about how pop has changed and what made her such an intriguing star to begin with.

Despite rising to prominence on the crest of the early-2000s idol revival as part of Morning Musume's Hello Project network, Matsuura occupies a space in the public consciousness that's somewhat removed from the core of what people think of as "idols." For one thing, she can sing, having carved out a post-idol career of sorts as a jazz singer. This is an important part of her appeal, contrasting to the consciously amateurish style of many contemporary idols.