Warthur
If Fourth captured the Soft Machine drifting towards pure jazz territory, Fifth sees them having travelled most of the way there. With Robert Wyatt having been jettisoned, the first half of the album sees temporary replacement Phil Howard on drums, with his replacement John Marshall (who would be the sole member of this lineup to survive to the very end of the band's career) taking over on side two. As well as losing Wyatt, the band also appears to jettison most of its connection to the Canterbury sound with this album, with the music being gentle, quasi-ambient fusion showing a clear influence from In a Silent Way, with Mike Ratledge's keyboards at points taking on a quasi-New Age sort of sound - as can be heard on Drop. Personally, I tend to regard this album and Fourth as being a failed stab at establishing respectability amongst the jazz establishment - as I said about the Fourth, often the music here sounds more conventional and less interesting than a lot of fusion worked made by highly respected jazz musicians of the era. Following this one, a few rock elements would return to the band's music, bringing them closer to the jazz-rock fusion mainstream.
As it is, Fifth is an album which will presents nothing whatsoever that is related to the Canterbury sound, won't excite fusion fans, and isn't likely to convince jazz fans either. It captures the Softs in the act of essentially abandoning their earlier audience in the hope of finding a different one, only to produce an album incapable of pleasing anybody. It's not flat-out incompetent and it's probably worth a listen if you are a major fan of the Softs, but there are many better Canterbury albums, many better fusion albums, many better jazz albums, and a good number of better albums that mix all of those three styles together than this one.
And in the last category, to illustrate the failure of the Softs' Fourth/Fifth-era approach, I'd include Matching Mole - which is, of course, Robert Wyatt's first post-Machine album. That just about says it all really. Thankfully, the band would undergo another evolution in time for Six, which improved its fortunes immensely and is probably responsible for allowing it to survive as long as it did; I think another album in this vein would have killed Soft Machine stone dead.