The Bassballs Twin Dynamic Envelope Bass Filter Pedal from Electro-Harmonix is an envelope filter in a compact guitar pedal. The vocal sound of its two sweeping filters gives bass a strong presence under leads, or a commanding quality when out front. The resonant frequencies are engineered solidly into the full range of the bass guitar's strongest harmonics. The envelope filter will respond to every bass note. The sweep is widely variable and harmonic enrichment is available with the Fuzz option.