Royal Holloway is great for Music. The Music Department has an excellent academic reputation, which is well deserved; it is rated 5* for research, and as a former student there I can testify that the teaching is really good. It offers a wide range of units, which cover all the main areas of musicology (historical musicology, ethnomusicology, theory & analysis), performance and composition. The majority of units are quite traditional, though you can do units/half-units on topics such as music technology, film music, popular music and so on if you want. The offer for single honours Music, 2008 entry, is AAB.
Performance isn't compulsory, even in the first year, but if you do want to specialise in it then there is ample opportunity. If you are good enough then you can get instrumental lessons at the Royal College of Music, and in order to get onto any of the specialist performance units you have to pass a stringent audition. If you enjoy performance but aren't good enough to specialise, then there are loads of performance opportunities available in the many ensembles (Symphony, Chamber, String and Baroque Orchestras, University Chorus, Chamber Choir, Chapel Choir and Schola Cantorum within it, Big Band and Pheonix, plus an Andean band and a gamelan orchestra!). The Music Department runs a packed concert calendar.
In addition, the Department is close-knit, warm and supportive. The main building (Wettons Terrace) must be Edwardian at the latest, but the facilities themselves are up-to-date. There's a well-stocked music library with a PC lab in the department building, which is handy for last-minute dashes to hand in essays...