This is one of many possible metronome configurations using the 555. We found it in an Electronics Now from the 90s. The transistor can be any general purpose. For greater power powered with 9 or 12 V use the BD135.

This is one of many possible metronome configurations using the 555. We found it in an Electronics Now from the 90s. The transistor can be any general purpose. For greater power powered with 9 or 12 V use the BD135.