drum
鞉 centers on a drum, specifically a small hand-held drum used in traditional settings. The meaning is narrow and concrete.
鞉 combines 革 (leather) with 兆, which likely provides the sound. The character refers to a small leather drum, consistent with the leather radical.
The left side 革 means leather, and the right side 兆 looks like a drum on a stand with a mallet. Picture a small leather drum being struck.
For トウ, imagine the drum making a deep 'toe' sound when hit: toe -> トウ, and the leather drum resonates.