The Fall Sertoma Series presents Montana Skies at 3 p.m. Sunday at Sertoma Amphitheatre in Cary's Bond Park, 801 High House Road. The duo combine cello, electric cello and guitar to get a sound somewhere between an orchestra and a rock band. The concert is free. For more information, call 919-319-4560 or visit montanaskiesmusic.ning.com.