(Bracing myself for the snarky comments...but here goes).

I've never really been much of a rap/hip-hop consumer, so I guess it's no surpise that I didn't know this; but was surpised by how many rappers in the 90's were sampling Prince's work. It's like in the 90s some viewed Prince as out of step, chasing the rap game, being irrelevant, and yet those who were alledgely "de-throning" him were busy using his music. Like they weren't talented enough to do anything really originally, but werre getting all the buzz. Absolutely loved, loved, loved Tennesse....but didn't really care for Alphabet Street and am sooooooo embarassed to admit that I didn't realize/know that Tennesse sampled AS until I read it in an article.

Which led me to wonder: did Prince get paid when these people sampled his music, did they have to get his permission, or did it depend on if the music being sampled was owned at the time by him or Warner Bros

Asenath said:

Prince and WB got paid when the samples were declared, which became standard circa 1992-93 but wasn't often the case before that (Prince himself would sometimes sample other artists without getting a licence up until 1992). Check the liner notes of any given album or song to see if a sample was declared or not: if so it would usually say "courtesy of WB" and declare Prince as a co-author).
I believe sampling licences are usually more or less an automatic process if only because of the sheer amount of licences majors have to process and the fact that it's an effortless source of income for both labels and songwriters. However some artists do the original artist the courtesy of asking permission. WB records would have had to be licenced by WB for as long as they owned the masters of a recording, but as both the recording (usually owned by the label) and the composition (usually owned by the artist via a publisher) are used, both get paid. On the other hand I'm not aware of any NPG Records era authorized sample and I suspect Prince wouldn't have allowed them. I may not be entirely accurate on some technicalities so someone correct me if I'm wrong.
[Edited 9/29/18 11:49am]

I still own this one by Grandmaster Melle Mel and Van Silk. It samples the "What´s the matter with your world?" part from Pop Life and the "Oh yeah !" part off of Sign o the Times. I doubt that they cleared the samples back then. This came out around 1989, before the huge Biz Markie lawsuit.