There is no doubt they helped put things in perspective; I would hope she was a keen listener.
He was a keen listener and had not missed the fact that Elminster had left Cyric's name out of his last statement.
And he is a keen listener.
These 'sample moments' are often explicitly mentioned in the archives, but there are a lot of hidden ones; Treasures for the keen listener.
The keenest listener could not have trailed the progress of The Shadow.
As an adult, he doesn't use a hearing aid; instead, he has become a keen listener.
A really keen and paranoid listener would have reflected that anything Lord Vetinari said aloud even while he was alone might not be totally worth believing.
But she is also a keen listener.
A really keen listener would have heard the faint whirring and ticking inside the walls.
However, a keen listener could notice a slight change in the tempo of the song.