never seen this in a roland keyboard

[fantomCK]

Envelope Looping (out of jupiter 80 parameter guide - page 36)

Loop Mode
Use this to loop the envelope between certain regions during a note-on.

FREE-RUN When the Decay segment has ended, the envelope will return to the Attack. The Attack through
Decay segments will repeat until note-off occurs.

TEMPO-SYNC Specifies the loop rate as a note value (p. 86) (Sync Note parameter).
Returns to the Attack at the specified rate. If the Attack+Decay time is shorter than the specified
rate, the Sustain Level will be maintained. If the Attack+Decay time is longer than the specified rate,
the envelope will return to the Attack even though the Decay has not been completed. This will
continue repeating until note-off occurs.