[RTTY] Warble at beginning of RTTY macro

[Charles Lind]

During the CQ WW I had one station return to my call, and for about the
first second of his transmit there was a warble that sounded vaguely like
SSTV, then a readable macro followed.  I emailed the ham, and he
volunteered he had made very few RTTY QSOs, he was using HRD set to LSB,
not RTTY.  I have not heard this odd combination before: what was the odd
"mode" that preceded the RTTY?  And how did it get there??
Tnx and 73, Chuck, N8CL