Definition of Hummding (Oxford Illustrated Dictionary)

Humdinger: of remarkable excellence, that is extraordinary
perfection of a kind
one having no equal

Whan a bell is struck ("ding"?),the vibrations are compound, that is, we
experience not just the vibration of that tone, known as the Strike Note,,
but also its accompanying overtones, and( most significantly for Hummding
Teams)..... the deep tone that persists after these have died away.....known
as the Hum Note.
(taken from The Concise Oxford Dictionary of Music)

Similarly, Hummding Teams are made up not simply of talented
individuals sounding their own confident note, but perform also as a group
of inseparable harmonious sounds with a residual depth which persists after
their Hummding Day has ended.

Fine-Tune: to bring into the most efficient working order by especially fine
adjustments

to draw out to a fine degree of fineness

Finesse: delicate manipulation