Echo <concept> <anything>:

do <concept> <anything> then do <anything>. That is, do whatever is called, then drop the first concept and do the call again.

For example,

1.  Echo Tandem Swing Thru: (from Parallel Waves)

Tandem Swing Thru then Swing Thru.

2.  Echo Cross Concentric Mix: (from a Tidal Line)

Cross Concentric Mix then Mix.

3.  Echo Checkpoint Recycle By Turn Thru: (from a R-H Tidal Wave)

Checkpoint Recycle By Turn Thru then Turn Thru.

(in this case, the <concept> is "Checkpoint Recycle By".)

4.  Echo 6 By 2 Acey Deucey: (from R-H Twin Diamonds)

6 By 2 Acey Deucey, then Acey Deucey.

5.  Echo Crossover Circulate: (from Parallel Two-Faced Lines)

Crossover Circulate then Circulate.

6.  Echo Centers Partner Tag: (from Parallel R-H Two-Faced Lines after the Centers Counter Rotate 1/4)

Centers Partner then (all) Partner Tag.

Note that in the last 4 examples, what is dropped (e.g., 6 By 2, Crossover, Centers) may or may not be considered a concept.

P.S., several months ago, I was working on a Ceder Chest style definition for Echo, but I had too many unresolved questions, so I temporarily stopped working on the definition. One problem, in particular, is trying to determine what the 'concept' is. For example, why isn't "Echo Split Phantom Lines Circulate" a "Split Phantom Lines Circulate then Phantom Lines Circulate"?