Allman Brothers: "Blue Sky"
One of the greatest guitar solos ever, this ur-jam-band tune seems to roll on and on, relaxed and sure of itself, perfectly illustrating the lyrics and the scene of the song: a walk along a country road, the sun out, the birds singing, and all right with the world.

Bach: 5th Brandenburg Concerto (BWV 1050), 1st movement (Allegro)
The harpsichord builds and builds after an immensely long, involved, sinuous solo ... there's the briefest pause ... and the violins enter with the main melody to finish the piece. Rarely is anticipation so expertly constructured and so perfectly rewarded.

Talking Heads: "Once in a Lifetime"
A prime example of nervous white-folk funk, but it's really the buzzsaw grinding guitar that finally sneaks in during the last 45 seconds or so that makes the song.