Final answer:
Eric Clapton was the electric guitar great who contributed significant improvisational skill to the sound of the British acid rock band Cream.
Step-by-step explanation:
The British acid rock band Cream featured plenty of improvisation by the electric guitar great Eric Clapton. Cream was known for their fusion of blues, psychedelic rock, and hard rock, and Clapton's guitar playing was central to their sound. His improvisational skills and innovative techniques contributed greatly to Cream's musical legacy, with songs like 'Sunshine of Your Love' and 'White Room' showing off his guitar prowess.