This source is just src/gtkvumeter.c/h
The configure script is for a simple test program that is included for your amusement. It also shows all the functions of gtkVUMeter.
API
GtkWidget *gtk_vumeter_new (gboolean vertical); void gtk_vumeter_set_min_max (GtkVUMeter *vumeter, gint min, gint max); void gtk_vumeter_set_level (GtkVUMeter *vumeter, gint level);
There is much more in the header. Hopefully this thing does everything you could ever want. Also check mumblelina.com for the complete API.