Instruct: Classify a given review into positive or negative sentiment.
Query: A colorful and idiosyncratic guide to progressive music.

Bradley Smith defines "progressive music" quite broadly, encompassing progrock and fusion, but also ambient, new age, avant-garde and experimental, and even indie thrash and industrial. Progrock purists will be enraged by some omissions and dubious entries in his progressive "canon," but most readers will make some surprising new discoveries. The writing is engaging, and Smith includes a number of useful appendices of source information.