If you're not going to be able to make Semana Santa (Holy Week) or don't want to face the crowds, to at least get a feel for it head to La Torre del Oro in the evening (8pm+) to spot the band practicing. No matter what time of year (even when the event has only just past) they are there trumpets-a-tooting, drums-a-banging.
Another spot is in the Maria Luisa Park, not too far from the Plaza de Espanya entrance.
Paseo Cristobal Colon S/N, 41001 Sevilla, Spain
+34 954 22 24 19
Google map: bit.ly/nUjWjR