Definition of "timbre"

It was a hard whisper to catch at first, since the grey moustache concealed all movements of the lips, and something in its timbre disturbed me greatly; but by concentrating my attention I could soon make out its purport surprisingly well.

1931, H. P. Lovecraft, chapter 7, in The Whisperer in Darkness

Quarterly the First quarter Siluer [...], The second Siluer a Cheueron gules betweene three Castles Sables And to his timbre vpon his healme, an Elephants head in his proper Colours […]

1492, "Confirmation of arms with difference and crest to Thomas and John Elyott by John Writhe, Garter, dated 7th July, 1492 (MS. queen's Coll. 139, No. 13.)", in 1925, Willoughby Aston Littledale, A Collection of Miscellaneous Grants, Crests, Confirmations, Augmentations and Exemplifications of Arms in the Mss. Preserved in the British Museum, Ashmolean Library, Queen's College, Oxford, and Elsewhere, page 70

The basilican pavilion [...] has frequently appeared on banners since the 13th century, but the pope has used it only rarely, as a timbre or crest above his coat of ARMS (a few examples exist from the time of MARTIN V).

2002, Philippe Levillain, John W. O'Malley, The Papacy: Gaius-Proxies, Psychology Press, page 1145