Martin Road Series | The built-in soundhole tuner available on the new Road Series. https://www.martinguitar.com/guitars/road-series/ | By Martin Guitar | Facebook
35 Acoustic Guitars With Offset Soundhole - And My Favorites - Guitaristnextdoor.com
Sound hole | Wiki @ Ultimate-Guitar.com
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Sound Hole Size, -Position and -Shape Influence the Sound - Stoll Guitars
Sound Hole Size, -Position and -Shape Influence the Sound - Stoll Guitars