When did Michael start working with Seth Riggs?

[analogue]

Can someone please tell me when Michael started working with Seth Riggs? Thank you

 

[WILL-I-AM]

I looked it up for you:
I found on youtube a interview of Seth Riggs on Michael Jackson.
And in that interview (2009 or 2010) he said 32 years ago, so it must have since around 1977 or 1978.
Here's the interview:

it's around 0:58

 

[Kirshach]

Seth seems to be a very nice guy, but as a vocal coach...