Here 'tis:
(0, 0, 0, [(key_clicked, key_t)],
[(get_player_agent_no, ":player"),
(agent_set_animation, ":player", "anim_strike_head_left"),
]),
(0, 0, 0, [(key_clicked, key_y)],
[(get_player_agent_no, ":player"),
(agent_set_animation, ":player", "anim_strike_head_right"),
]),
(0, 0, 0, [(key_clicked, key_f)],
[(get_player_agent_no, ":player"),
(agent_set_animation, ":player", "anim_ready_slashleft_staff"),
]),
(0, 0, 0, [(key_clicked, key_g)],
[(get_player_agent_no, ":player"),
(agent_set_animation, ":player", "anim_ready_slashright_staff"),
]),
----------------------------------------------------
Stick that in an aprropriate bit of a mission template, and the player will be able to shake his gory locks by pressing T, Y, F, and G in quick sucession. Works best in "default town visit" for me, but if you want to do a celebratory mosh on the battlefield by putting it under "lead_charge" it's up to you. I'm hoping to improve the dance moves when I figure out animation editing better.
The credit for this should go to Slawomir of Aaaaargh, without whom I never would've realised how easy it is to make an M&B character get their groove on.