Deep Note
The Deep Note had originally been from a soft to a loud pitch. Over the years it has been remixed digitally which made the Deep Note with a more abridged sound. Beginning in 1988 the Deep Note became louder and abridged. In 1993 the Deep Note was cut short to save time for Laserdisc (1995 for VHS). Most recently, however, the Deep Note has been cut short to the single note (where both sounds stay in one pitch). This is in favor of other sound effects in certain THX logos.