808 Cowbell
On the 808 2 pulse waves go through independent VCAs. They are then mixed together and go through a band pass filter. You can simplify this by using a single VCA after the bandpass filter.
Use a square wave for both oscillators. Switch to triangles / sines for a more muted sound.
The oscillators on the 808 are tuned to about 540Hz and 800Hz. The Sound On Sound article on cowbells says 587Hz and 845Hz but different articles list different frequencies. I’ve used C5 and G5. Play with detuning to get a more inharmonic sound. Keep the higher one slightly louder in the mix.
Use a bandpass filer with moderate resonance. Try BP2 and BP4. BP2 will be brighter. Different combinations of pitches will be most clangorous at different filter frequencies. Play with the filter frequency until it’s right.
Different notes will be more or less convincing. Try starting with C3.
Use an AR envelope with a very short attack and moderate release. Don’t use envelope modulation on the filter, only on the VCA. You want the sound to be dull and clangorous not bouncy.
Modifications:
If you want a more realistic sounding cowbell, turn up the ring modulator in the mixer. This will give it a more metallic sound.
Play with the octave settings to find different metallic and bell sounds.
Further Reading:
Sound On Sound, Synth Secrets: Synthesizing Bells
Sound On Sound, Synth Secrets: Synthesizing Cowbells & Claves