Biggest Music Concert ever?

Just doing my surfing thing today and I come across a page stating that the SARS concert with the Rolling Stones headlining in Toronto, July of this year, was the biggest music concert ever with about 500,000 people attending.
Now I realise that this is a LOT of people for such an event but I was sure that in 1991 AC/DC pulled in 1,000,000 people at a concert in Russia. They had planned to hold in in Red Square but was moved to an airstrip when they realised how big it was getting.
Does anyone have the definitive answer concerning the biggest ever?

I remember hazily that Simon and Garfunkel’s 1981 (?) reunion concert in New York’s Central Park held the contemporary record for biggest concert attendance. I’ll have to seach for just exactly what the attendance was. I’m thinking 800,000–1,000,000, but that seems a bit high.

AC/DC’s 1991 show in Russia may well have surpassed S&G’s Central Park concert, but not many other shows are in the neighborhood of those two.

From www.guinnessworldrecords.com :

What they didn’t have was largest rock group concert. The website isn’t all inclusive of their records, so there may be rock group attendence record out there.

Wow. I can’t even get my brain to picture what that must have looked like !

The Toronto concert was a paid event, so this would hold the record for paid attendence, it would seem. I’ve heard of a bunch of free concerts such as Paul Simon’s concert in Central Park, which played to certainly more than 500 000. The problem is that these events must have estimated attendance whereas paid events can just count the tickets.

I’m pretty sure the largest ticketed/paid rock concert/event ever held was the 1973 Summer Jam festival held at the Grand Prix Raceway in Watkins Glen, New York. It was a single day music festival featuring The Greateful Dead, The Allman Brothers and The Band. Over 600,000 people were in attendance.