In a silent way, Miles Davis (Columbia Records, 1969)

It didn’t swing, the solos weren’t even a little bit heroic, and it had electric guitars... But though In a Silent Way wasn’t exactly jazz, it certainly wasn’t rock. It was the sound of Miles Davis and Teo Macero feeling their way down an unlit hall at three in the morning. It was the soundtrack to all the whispered conversations every creative artist has, all the time, with that doubting, taunting voice that lives in the back of your head, the one asking all the unanswerable questions
— Phil Freeman

A few days ago I read a review in The Economist about a book I'm going to buy, How to listen to jazz (Ted Gioia, Basic Books) that argues that the reason why jazz isn't a 'popular' art-form and is considered to be 'esoteric' is that listeners don't know how to listen to it, don't know how to distinguish what makes one piece of music good, and another great. This detail from the review jumped out at me:

The best jazz musicians do not worry about producing clearly defined notes (the do-re-mi system that structures Western classical music). Instead they look to make particular sounds - bending notes and creating unusual timbres - which is a consequence of the heavy African influence of jazz.

The reviewer then goes on to add that the 'emphasis on sound over notes' is especially pronounced in Coltrane's late work. But jazz, as an art-form, is also deeply important for the way the record - the extended listening experience - is central, where listening to a great jazz record is always about experiencing music over time, where recent memories of what came before provides context for what is happening now.

Miles Davis's In a silent way (1969) is an exciting record on many, many different levels: for the overall recording sound, as the album that prefaced the artist's 'electric' period; for the grace and intelligence of the musicianship (Chick Corea's first appearance on a Davis record, Herbie Hancock, Joe Zawinul, Wayne Shorter, Dave Williams, Tony Holland); for the way it sought to meld the radically new musical idiom of funk with jazz, directly influenced by the musical connections and knowledge of Davis's younger partner who later became his wife, 'Mademoiselle (Betty) Mabry' and as a record that is made up of strikingly different musical experiences. 

(For info on how the later Betty Davis linked Miles with younger musicians of the era for this record and the later so-called 'The Columbia Years, 1968-1969 sessions, see this article by Dominique Leone, published in Pitchfork in 2001)   

According to a critic the record is also distinguished by the editing/arrangement of producer, Ted Macero who incorporated 'elements of the classical sonata form' on the record: 

Macero’s editing techniques have incorporated elements of classical sonata form in Davis’ recordings for In a Silent Way.[9] Both of the extended tracks on the album consist of three distinct parts that could be thought of as an exposition, development and recapitulation. The last six minutes of the first track are actually the first six minutes of the same track repeated in exactly the same form. With this “trick” the track takes on a more understandable structure.

In a silent way is conceived a musical experience of two distinct parts ('Shhh/Peaceful' and 'In a silent way/It's about time') of about equal time; 18'16 and 19'52 respectively. But as with any great jazz album, the music is to be experienced with the knowledge of the whole, what has come before and after. My favourite section of the record (part four, 'It's about that time') gets its power to surprise and delight because it differs from the rest, while deeply resembling it - it's a development and consolidation at the same time.

In this sense the 'echo' is within us, as part of our listening experience, held in our memories of what we have heard before. 

Following an almost mathematical precision of one minute intervals, the funk-groove refrain comes in around 1'30, builds than disappears to come back one minute later (and then another; the keyboards at 4'30 and at 6'30 the drums/percussion lifts it up, with such force it's a beautiful thing).    

The critical reception In a silent way was mixed, even though it was Davis's first album to reach the Billboard chart since My Funny Valentine in 1965.  People tended to hear reflections of their own musical bias, or preference when responding to the work.

A good example of this is the review by the ever-expressive enthusiast Lester Bangs from Rolling Stone who celebrated the record for its psych-rock feel, even likening it at one point to the Stones's trippy '2000 light years from home' ...

From the Lester Bangs' Rolling Stone review

The songs are long jams with a minimum of preplanned structure. That they are so cohesive and sustained is a testament to the experience and sensitivity of the musicians involved. Miles’ lines are like shots of distilled passion, the kind of evocative, liberating riffs that decades of strivers build their styles on. Aside from Charles Mingus, there is no other musician alive today who communicates such a yearning, controlled intensity, the transformation of life’s inchoate passions and tensions into aural adventures that find a permanent place in your consciousness and influence your basic definitions of music.

Check out this informative article on the record by Nenad Georgievski, published on the All about Jazz website a few years ago that considers the importance of the record and role played by the various musicians featuring on it.