Given the following context:  "The Thing That Should Not Be" was inspired by the Cthulhu Mythos created by famed horror writer H.P. Lovecraft, with notable direct references to The Shadow Over Innsmouth and to Cthulhu himself, who is the subject matter of the song's chorus.  It is considered the heaviest track on the album, with the main riff emulating a beast dragging itself into the sea. The Black Sabbath-influenced guitars are downtuned, creating slow and moody ambiance. "Welcome Home (Sanitarium)" was based on Ken Kesey's novel One Flew Over the Cuckoo's Nest and conveys the thoughts of a patient unjustly caged in a mental institution. The song opens with a section of clean single strings and harmonics. The clean, arpeggiated main riff is played in alternating 44 and 64 time signatures. The song is structured with alternating somber clean guitars in the verses, and distorted heavy riffing in the choruses, unfolding into an aggressive finale. This structure follows a pattern of power ballads Metallica set with "Fade to Black" on Ride the Lightning and would revisit with "One" on ...And Justice for All."Disposable Heroes" is an anti-war song about a young soldier whose fate is controlled by his superiors. With sections performed at 220 beats per minute, it is one of the most intense tracks on the record. The guitar passage at the end of each verse was Hammett's imitation of the sort of music he found in war films. The syncopated riffing of "Leper Messiah" challenges the hypocrisy of the televangelism that emerged in the 1980s. The song describes how people are willingly turned into blind religious followers who mindlessly do whatever they are told. The 136 beats per minute mid-tempo riffing of the verses culminates in a descending chromatic riff in the chorus; it increases to a galloping 184 beats per minute for the middle section that climaxes in a distorted scream of "Lie!". The title derives from the lyrics to the David Bowie song "Ziggy Stardust". "Orion" is a multipart instrumental highlighting Burton's bass playing. It opens with...  answer the following question:  What song has mid-tempo riffing, followed by a bass solo at half-tempo?
A:
Orion