"Thank You" signalled a deeper involvement in songwriting by singer Robert Plant: it was the first Led Zeppelin song for which he wrote all the lyrics. According to various Led Zeppelin biographies, this is also the song that made Jimmy Page realise that Plant could now handle writing the majority of the lyrics for the band's songs. Plant wrote the song as a tribute to his then-wife Maureen.
The song features Hammond organ playing by John Paul Jones, which fades into a false ending before concluding with a crescendo roughly ten seconds later. This has created a problem for radio stations wishing to play the track, which must decide whether to accept the dead air or cut it off. Some stations run an edited version with the silence eliminated. For the recording of this track, Page played on a Vox 12-string guitar. It was also one of the few Led Zeppelin songs on which Page sang backing vocals.
When "Thank You" was performed at Led Zeppelin concerts, it featured Jones' extended keyboard solo (either on the Hammond organ or on some 1972-73 versions, the Mellotron) as an introduction to the song. The piece was eventually dropped from the band's standard live setlist following the 1973 tour of the United States, when it was only occasionally used as an encore, for example, at the tour's final concert in Madison Square Garden.
In a retrospective review of Led Zeppelin II (Deluxe Edition), Michael Madden of Consequence of Sound praised the remastering of "Thank You", believing the track now sounds "mellow and well-balanced". Madden further praised the remastering, writing the track "breathes easy during the verses and ascends elsewhere in the song", along with "illuminating Page's touch and Bonham's haymakers". When reviewing the added bonus tracks of the Deluxe Edition, Madden further praised the new version of "Thank You", titled "Thank You (Backing Track)", writing the track "magnifies the song's tasteful sheen, popping with Bonham’s drums and Jones’ organ, which seems to have a mind of its own."
In November 2010, "Thank You" topped Gibson's list of "Top 10 Thanksgiving Songs". The song was recorded by Page and Plant for the No Quarter: Jimmy Page and Robert Plant Unledded album. It was released as a single and reached number eight on Billboard magazine's Album Rock Tracks chart in 1995.
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