Final answer:
The electric guitar is the instrument that most transformed rock from its early dependence on piano-based instrumentation.
Step-by-step explanation:
The instrument that most transformed rock from its early dependence on piano-based instrumentation was the electric guitar.
The combination of electric instruments with the sounds of gospel, blues, country, jazz, and R&B gave birth to the new sound of rock and roll. The electric guitar's ability to produce loud, distorted, and sustained sounds played a major role in shaping the genre. Its popularity soared with iconic guitarists like Jimi Hendrix, Eric Clapton, and Jimmy Page.