Tombo (The Cottage of Lost Play):

The gong standing outside the Hall of Play Regained inside the Cottage of Lost Play. It is also called 'The Gong of the Children' and it is rung to summon them to meals and to tale-telling. It is rung once for a call to meals and three times for story-telling.

The Book of Lost Tales One (HoME.I)
The Book of Lost Tales Two (HoME.II)
The Lays of Beleriand (HoME.III)
The Shaping of Middle-Earth (HoME.IV)
The Lost Road and Other Writings (HoME.V)
The Return of the Shadow (HoME.VI)
The Treason of Isengard (HoME.VII)
The War of the Ring (HoME.VIII)
Sauron Defeated (HoME.IX)
Morgoth's Ring (HoME.X)
The War of the Jewels (HoME.XI)
The Peoples of Middle-Earth (HoME.XII)