The Grand Auditorium size (also known as Martin M or Martin 0000 guitars) is like a 000 with an extra-wide bottom bout for added volume, and a long-scale neck for added power and projection. Our friend Spoon Phillips feels a Martin M sounds like a Dreadnought that had the EQ on the bass pulled down more I line with the other strings, giving the voice a punchy mid-range. And many others consider it a good alternative the boxier Dreadnought size. Not as well-known as other sizes, the M has its devoted fans, including Richie Sambora, David Bromberg, Arlo Guthrie, Jorma Kaukonen, Woody Mann, Shawn Colvin, and Beatles producer Sir George Martin. And all of them have been honored with a Martin signature model using this body size.