There was a device around in the States about 10 years ago to which you could have your brand new guitar attached, and it would vibrate at a frequency which, it was claimed, would age the guitar overnight, with a consequent improvement in tone.

IIRC Rick Turner, the well known guitar maker had a hand it its development, and I further seem to remember that it was endorsed by no less than Jackson Browne, who had his guitar treated on the machine.

Haven't heard much of it lately, however ...