The embracing arm is rigid, and fixed to open the greatest amount of
distance between the partners. Clasped hand is white-knuckled with tension,
but the rest of that arm is loose and moves up and down or pistons back
and forth. The posture is wobbly or bent forward at the waist. Line of
dance is a "theoritical concept".
Conversation: (man) "Are you in the cross?"
(woman)
"Where do I step now?"
Found: In Intermediate classes, and stationary in corners
of the floor during the milonga or practica.
Steps under Study (click to see videos):

The embracing arm is rigid, but partners are close enough to perceive
body lead. Clasped hand is usually relaxed, but still rotates with respect
to frame. The posture is upright and the couple is generally moving with
the woman back to the line of dance. Man knows how to maneuver in corners
of dance floor, but either partner may suddenly halt the dance to "discuss"
the latest pattern just learned.
Conversation: (man) "Okay, NOW you do a back ocho..."
(woman)
"Sorry!"
Found: In Intermediate-Advanced classes, and stationary
at any point on the floor during the milonga or practica.
Steps under Study (click to see videos):

The man spontaneously creates patterns based on learned figures. The
embracing arm is relaxed, with firm pressure directed in a manner appropriate
to the step being performed. The clasped hand is relaxed and the frame
is solid (sometimes to the detriment of grace). The posture is upright
with beginnings of tango lean. The couple is moving generally with the
woman's right shoulder pointing towards the line of dance. May perform
"above the safety level" for the number of couples per unit area of floor.
Conversation: (man or woman) "Ooh, good one!"
(woman
or man) followed by "Excuse me!'
Found in: Intermediate-Advanced or Beginning classes, mostly
in line of dance, but sometimes in center of dance floor "showing off,"
during the weekend milonga or practica.
Steps under Study (click to see videos):

The man spontaneously creates patterns and figures based on genuine understanding
of the tango walk. The woman is able to take advantage of freedom provided
to make her own adornments. The frame is solid but relaxed and graceful.
The posture is straight with noticeable tango lean where appropriate.
The couple is moving generally with the "V" of their embrace following
the line of dance. Can make a simple pattern elegant and know more patterns
and figures than they use when dancing.
Conversation: (woman) "ahhhh"
(man)
low sigh of contentment. Man is silent
Found: Teaching Beginning, Intermediate and Intermediate-Advanced
classes, learning from professionals or teachers in/from Buenos Aires.
Too often found sitting at the edge of a packed dance floor filled with
stationary Beginners, debating Intermediates and show-boating Intermediate-Advanced
dancers.
Steps under Study (click to see videos):

The man "just walks", woman "just follows". May have forgotten why this
dance is so difficult to learn (because it's become second nature for
the professional). The posture, the frame, the movement and the embrace
are all elegantly graceful and suitable for pointing out as a shining
example to other levels of dancers.
Conversation: (silent, their expressions are in the dance)
Found: Dancing tango. Teaching tango. Selling and performing
tango. Breathing, talking, living tango.