— Constructor: music_node::music_node (void);
— Constructor: music_node::music_node (const unsigned int &b);

The constructor initialises the object and sets the number of bells in the rows that will be matched. If the default constructor is used, then the set_bells() function should be used to perform this action.

— Destructor: music_node::~music_node (void);

The destructor will go through the tree structure, deleting the sub-nodes of the current node.