Bell piece: Gangkogui is the Anlo-Ewe name for their double bells. Consider that these are hand made and as such, the sizes are at the discretion of the blacksmith who makes them. Obviously the large bells produce a low tone but are heavy and beyond a certain limit would be discarded in favour of a more manageable size. On the other end of the scale, smaller bells produce lower volume and tend to get lost in the ensemble. The point is, there are no fixed sizes or pitches, just the range between the extremes.In my experience with Ewe teacher Kobla Ladzekpo the value of a bell is not so much its absolute pitch but clarity of tone. In a hatsiatsia ensemble bells of various sizes were freely swaped between different parts - producing vastly different resultant melodies. The melodies produced in this music are subordinate to the rhythms of the parts.If you dig gangkogui you should also check out atoke bells. Here's the hatsiatsia to the Ewe music Atsia:

Atoke 1      x . x . x x . x . x . x
Atoke 2      x xx. x xx. x xx. x xx.
Gangkogui 1  . h l . h l . h l . h ll
Gangkogui 2  l l h h .h. l l h h .ll