Given the climb-anywhere nature of the southeast face of Greyrock and the fact that the most memorable part of any of the "Chipmunk" cracks on the southeast face of Greyrock are their starts, Alvin is as much a variation to Theodore as it is an independent line itself.
At the same grassy alcove where Theodore and Simon begin resides a wide, slightly right-angling crack. Alvin ascends this crack (5.5) for the first part of its first pitch (don't worry, no OW skills needed) before ascending broken cracks above (5.6) to lower angle ground (4th class). From here, any number of lines can be chosen to reach the summit of the massif, ranging 2 to 3 long pitches in length and generally covering easy terrain.
In the same alcove as Theodore and Simon, Alvin ascends the left-most crack and covers ground above to the sumit of Greyrock.
Wide gear, #4 Camalots, is necessary to adequately protect the first pitch of this climb. Some nut placements can be found in and around the crack, but they're finicky at best and not obvious. However, the climbing is very easy and rarely insecure.