Defines a symbol library entry. If name is used inside pick-symbol, then its definition is used, otherwise definition is picked randomly according to the template.
(lib-symbol piano1
'(a b c b d c (+12 b) de (+12 b) c (+12 b) c d b c))
(lib-symbol piano2
'(a b c d d c (+12 b) d e (+12 b) c (+12 b) c (+12 b) d))