On the violin and piano, he said, "Age enlarges and enriches the powers of some musical instruments--notably those of the violin--but it seems to set a piano's teeth on edge."

- Rambling Notes of an Idle Excursion

And, from the Museum of Musical Instruments, it appears that Mark Twain played a Martin!!!:

The C.F. Martin company is America's longest-running instrument manufacturer, building great guitars since 1833. Martin perfected the dreadnaught guitar, named after a WWI battleship design, during the 1930s, and its loud, booming voice and rich tone influenced the development of many styles of modern music. From Mark Twain to Shania Twain, nearly every notable musician who has ever picked up a guitar has played a Martin. Many of the earliest-made Martins are still in use today.

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