The tongue ‘holds’ itself quite correctly without any help – or rather, it does not hold itself at all – unless it is being misused by having to act as a false (unphysiological) opponent to any of the muscles of the larynx. 

Husler, Frederick, and Yvonne Rodd-Marling. Singing: the physical nature of the vocal organ: a guide to the unlocking of the singing voice. Vintage, 1976.