Martin Custom Shop “M” Grand Auditorium 28-Style Acoustic Guitar, Adirondack Spruce/Sinker Mahogany

The Martin Custom Shop “M” Grand Auditorium is a deliberate convergence of precision craftsmanship and informed design tradition. First introduced in the 1970s, the “M” body offered a wider lower bout than an OM or 000, borrowing its silhouette from archtop jazz guitars while maintaining a flatter back and thinner profile for better balance and playability. This particular Custom Shop iteration elevates that design with premium materials, heritage-forward details, and meticulous attention to build nuance—unsurprising from a long-standing collaboration between Martin and Russo Music, one of the few designated Custom Shop Expert dealers in the country.

The top is made from bound Adirondack spruce, a material chosen for its structural integrity and historical significance in pre-war guitar construction. The back and sides are cut from two-piece premium sinker mahogany—harvested and submerged decades ago, now recovered and air-dried for stability and aesthetic interest. Internally, the body is supported by a forward-shifted X-brace carved from Adirondack spruce to Golden Era scalloped specs at 5/16", reinforcing the top while allowing it to move in the right ways.

Ornamentation includes a herringbone top inlay, HD Zig Zag back purfling, and Style 28 Boltaron rosette—references to classic Martin styles from the 1930s. The gloss body finish and antique toner top bring it all together with vintage formality, while the satin neck promotes smooth movement across the fretting hand.

That neck is carved from select hardwood and shaped into a Modified V with Martin’s High Performance Taper with a 25.4" scale. A long diamond volute adds both strength and a visual callback to early 20th-century Martins. The fingerboard is black ebony with a 16" radius and abalone Diamond and Squares Long inlay pattern, and it joins the body at the 14th fret for full-range access. A matching ebony bridge houses a compensated bone saddle with 2 5/32" spacing.

With no electronics, the build remains fully acoustic—prioritizing resonance and mechanical simplicity. Grover StaTite tuners and a bone nut help to keep intonation stable as a table.

This Grand Auditorium isn’t trying to reinvent the wheel, but it does reassert the Martin Custom Shop’s reputation for thoughtful, historically anchored instruments. Whether you're a collector looking for an understated showpiece or a player in need of a responsive and balanced tool, this M model stands up to close scrutiny—both in the shop and on stage.