Natalie Gulbis matched Song's 66 to move into third place at 8-under-par 136. She is joined there by Grace Park (70), the Kraft Nabisco Championship winner. Mi Hyun Kim (67) and Jung Yeon Lee (66) are one stroke further back at minus-7.
Song picked up her first birdie when she stuck a 9-iron 15 feet from the cup at the par-4 fifth. She came back with a two-putt birdie at the next to get to 5 under.
Song, who turns 18 tomorrow, dropped a 9-iron some 10 feet from the cup to set up a birdie at the eighth. Song pitched her third shot to 15 feet at the par-5 13th and rolled in that effort to get to minus-7.
The 1999 U.S. Girls Junior Champion chipped in from just off the green at the par-3 16th. Song capped a bogey-free round when she drained a 15-foot birdie at the last at Eagle's Landing Country Club to grab a share of first.
'I played pretty well all day,' said Song, who has played the first 36 holes bogey-free. 'It was my last round as a 17-year-old, so I wanted to do it right. My putter was really good all day. My short game saved me a lot today.'
Kane began her round on the back nine and ran off six straight pars to start her day. She picked up her first birdie when she sank a 15-foot putt at the 16th. She found a fairway bunker off the tee at the next and could not save par from there.
The 39-year-old fought back with a two-putt birdie at the 18th to get back to minus-6. On the front side, Kane rolled home a 15-footer at the fifth for birdie.
She made it two in row when she two-putted for birdie at the par-5 sixth. Kane closed out her round with a 12-foot birdie putt at the eighth.
'I had some chances early on,' Kane said. 'Made a good birdie on No. 16, then followed it with a bogey on 17. I birdied 18, but then left a few on the front nine. A real solid day of hitting the ball and staying very patient.'
Isabelle Beisiegel and Rosie Jones each posted 66s to join Reilley Rankin and Michele Redman, who both shot 68s, in a sixth-place tie at 6-under-par 138.
Overnight leader Christina Kim slipped to a 2-over 74. She fell to minus-5 where she is joined by seven other golfers, including Se Ri Pak, the defending champion, who carded a 1-under 71 Friday.
Annika Sorenstam shot a 3-under 69 and is part of a group in 19th place at minus-3.
The cut line fell at 3-over-par 147 with 21 players advancing on the number for a total of 90 players making it to the weekend. Among those who missed the weekend were Moira Dunn (148), Beth Daniel (149) and Sophie Gustafson (150).