Presumably a son GAIA like the other Mountains
TMOLUS (Tmôlos). The god of Mount Tmolus in Lydia, is described as the husband of Pluto (or Omphale) and father of Tantalus, and said to have decided the musical contest between Apollo and Pan. (Apollod. ii. 6. § 3; Schol. ad Eurip. Or. 5 ; Ov. Met. xi. 157.)
Source: Dictionary of Greek and Roman Biography and Mythology.
CLASSICAL LITERATURE QUOTES
Pseudo-Hyginus, Fabulae 191 (trans. Grant) (Roman mythographer C2nd A.D.) :
"Midas . . . was taken as judge at the time when Apollo contested with Marsyas, or Pan, on the pipes. When [the mountain-god] Timolus (Tmolus) gave the victory to Apollo, Midas said it should rather have been given to Marsyas. Then Apollo angrily said to Midas : ‘You will have ears to match the mind you have in judging,’ and with these words he caused him to have ass's ears."
Ovid, Metamorphoses 11. 150 ff (trans. Melville) (Roman epic C1st B.C. to C1st A.D.) :
"The crags of Tmolus, steep and wide and high, gazing across the sea, at one side fall to Sardis, at the other reach their end at small Hypaepae. There Pan sang his songs, flaunting among the gently Nymphae (Nymphs), and played light airs upon his pipes, and dared to boast Apollo's music second to his own, essaying with old [mountain-god] Tmolus as the judge unequal contest. On his mountain top the judge was seated; from his ears he freed the forest trees; only a wreath of oak fringed his green locks, with acorns dangling round his hollow temples. Then, looking towards the shepherd-god, he said, ‘The judge attends.’
So Pan made music on his rustic reeds and with his uncouth song entranced the king. Midas by chance was there. To Phoebus [Apollon] next grave Tmolus turned and, as he turned, his fringe of trees turned too. Apollo's golden hair was garlanded with laurel of Parnassus; his mantle, rich with Tyrian purple, swept the ground he trod; in his left had he bore his lyre, inlaid with gems and ivory; his right the plectrum held; his very pose proclaimed the artist. Then with expert touch he plucked the strings and, won by strains so sweet, old Tmolus bade the reed bow to the lyre. The sacred Mountain's (Mons) judgement and award pleased all who heard; yet one voice challenging, crass-witted Midas' voice, called in unjust."
- Hyginus, Fabulae - Latin Mythography C2nd A.D.
- Ovid, Metamorphoses - Latin Epic C1st B.C. - C1st A.D.