While in Viseu I discovered and purchased a music CD of a Portuguese singer named Dulces Pontes. If you are planning a trip to Portugal I highly recommend that you purchase this CD titled "caminhos" (which is available on Amazon etc.) I guarantee it will get you geared up for your visit.
I have since purchased several other CDs by this same artist. She has a beautiful haunting voice. The songs she sings are traditional and traditionally inspired. There is a lot of Celtic influence in Portuguese music (the ancient Celts were settled in Portugal at one point in history) but it is also bound together with Moorish and Spanish sounds.
I know this is a travel forum, but for me at least, music is a big part of my travel experience, and I make of point of purchasing music from all of the places I visit. It's great to pop Dulces Pontes on the CD player on a gray and gloomy winter day and remember the fantastic trip we had not too long ago.