What is Hoover sound?
The hoover is a growling, sweeping synth sound — originally from the Roland Alpha Juno's "WhatThe?" patch — famous from early rave and hardcore, and revived heavily in modern hard techno leads and basses.
The characteristic "vacuum cleaner" texture comes from detuned sawtooth-like oscillators with a strong pitch envelope, PWM-style movement and chorus. To recreate it, stack detuned saws, add a fast downward pitch sweep at note start, apply chorus and distortion, and play it in minor-key riffs. Hoovers work both as lead riffs and, pitched down, as aggressive bass textures.