From bowiki

The Tuning System used on a modern bodhran is a combination of mechanical elements providing adjustability to the tension of the drum's skin.

Tuning Systems fall into three main categories defined by the positioning of the Tuning Adjustment Hardware. Such hardware takes many varied forms.

• Internal - where a Tuning Ring carrying a Bearing Edge is mounted inside the drum shell and Tuning Adjustment Hardware is mounted internally

• External - The main shell carries the bearing edge and the tuning adjustment hardware is mounted externally

• Integral - The Bearing Edge is built into or a lateral extension of the Shell and the tuning adjustment hardware is contained within the shell walls