Here's some live tape from when they played the Fillmore West in '67
http://tinyurl.com/6e4yzux
My memory says that when they played, since most of the musicians at the time were hired hands, they used music stands. I think the original record was just studio guys, then they had to put a band together.
You are correct. That audio reflects their folk rock/garage band sound before it shifted in '68 to the slicker production with horns added.
A fact I did not know: "From 1967 to 1972, The Grass Roots set a record for being on the Billboard charts for 307 straight weeks. They are one of only nine bands that have charted twenty nine or more Top 100 Billboard singles." And we'll have to fact-check this: "They hold the all time attendance record for a one act, the US concert of 600,000 people on July 4th, 1982 in Washington, DC."
More info:
http://the-grassroots.com/html/biography.html