Complex sentence: The sounds used for it used to be pre-recorded, but when a technical fault prevented the recording from playing, voice actor Mel Blanc himself improvised the sounds of the sputtering car starting up in a performance received well enough for him to continue the role permanently.
Split into simpler sentences: The sounds used for it used to be pre-recorded, but when a technical fault prevented the recording from playing, voice actor Mel Blanc himself improvised the sounds of the sputtering car starting up. His performance was received well enough for him to continue the role permanently.