I've always been a big fan of Doobies, especially of their vocals, and you'll hear some of the secret to their vocal sound on this video.
1) The first thing you notice is the guitar layers. There are two electric guitars that are doubled playing the main chordal phrase, and 3 different acoustic guitars that add both counterpoint and motion.
2) Even though the Doobies are known for their dual drum kit sound, this song has only one kit that's recorded very old school on only 3 tracks - kick, snare and overhead. The stereo spread comes from the 3 tracks of percussion - tambourine, and 2 different conga patterns.
3) Tommy Johnson's vocals are on a single track, while the chorus harmonies consist of two tracks of 3 part harmonies (their signature vocal sound) and a track of gang vocal on the lowest part.
4) The harmonica solo is track-shared on an empty section on two of the background vocal tracks, a practice that was almost standard back in the tape days. Take notice to the difference in levels. In the final mix, it sounds like they used most of the loud one with a few phrases from the quiet one.
5) The outro ad lib lead vocal lives on the lead vocal track, with a second pass on one of the background vocal tracks, again employing track-sharing.
6) Everything you hear was done on only 15 tracks!
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