Not quite what he's looking for. You can add more variety to make a station of music that includes x OR y OR z, but you can't make a station that plays songs with x AND y AND z.
I've run into this as well. You try to make a station that plays piano rock, and Pandora goes "Hey, here's a song that fits! It has: 1) mixed acoustic and electric instrumentation, 2) major key tonality, and 3) mellow rock instrumentation." It won't care that every song you've added to the station was tagged with acoustic rhythm piano, all tags are equal to the matching algorithm.
I've run into this as well. You try to make a station that plays piano rock, and Pandora goes "Hey, here's a song that fits! It has: 1) mixed acoustic and electric instrumentation, 2) major key tonality, and 3) mellow rock instrumentation." It won't care that every song you've added to the station was tagged with acoustic rhythm piano, all tags are equal to the matching algorithm.