Classic Rock song with La vocal solo

[Arkanomen]

OK I think this is a classic rock song, as i heard it on the classic rock station. I have absolutly no idea who the artist/title is nor can I remember any lyric. : (
But heres the thing, It has a portion near the end of the song where the band cuts out and the singer goins into a meledy consisting of only the word "La". After which the band comes back in, plays a verse (i think) and then play some sort of instrumental finale. A line from the singer just came to me. During the final instrumental he comments somethign along the line of "So Good" or "Oh so good". Im convinced it sounds like AC/DC but im stuck and cant make the jump and find the song. Please help.

[Arkanomen]

anyone?

[atmaster]

AC/DC is not a staple group for Classic Rock stations.
Led Zepplin has a couple of songs with final lyrics about "feels so good"
The "La" chrous is throwing me for a loop

[jetstew]

It has to be "The Ocean" by Led Zep.