GR translation: jive accessory

[David Morris]

The woman's look essentially cuts Slothrop down to size (obliterates
his pretensions of being cool), and reveals that his "cool mouth harp"
doesn't make him cool.

On Tue, Apr 3, 2012 at 1:17 AM, Mike Jing <gravitys.rainbow.cn at gmail.com> wrote:
> P64.19-22  A woman turns to look at him from a table. Her eyes tell him, in the instant, what he is. The mouth harp in his pocket reverts to brass inertia. A weight. A jive accessory. But he packs it everywhere he goes.
>
> What exactly does "a jive accessory" mean here?