Highly fx filled, with a huge priority on experimental improvisation. It differs from improvisational jazz because it is usually created and performed with a "rock and roll attitude". Loud, crazy, and lots of beeps, boops, squeels, and distortion guitar and/or bass.
Due to the wildly eclectic nature of this genre, any given song can move from "palatable groove" to "psychotic aural nonsense" in seconds. Its not entirely about being noisy or weird, but it has no limits when it comes to where songs "go" during a live performance and even in the studio.
Sometimes referred to as "cartoon rock", spaceship rock is known to have been made popular by Drop Trio of Houston, an instrumental keys, bass and drums trio.