See Chapter XXII.
The word “tab” is vaudeville’s way of saying “tabloid,” or condensed version. While vaudeville is in itself a series of tabloid entertainments, “tab” is used to identify the form of a musical comedy act which may run longer than the average one-act musical comedy. Although a tabloid is almost invariably in one act, it is hardly ever in only one scene. There are usually several different sets used, and the uninterrupted forty-five minutes, or even more than an hour, are designed to give a greater effect of bigness to the production.
But the greatest difference between the one-act musical comedy and the burlesque tab does not lie in playing-time, nor bigness of effect. While a one-act musical comedy is usually intended to be made up of carefully joined and new humorous situations, the burlesque tab—you will recall the definition of burlesque—depends upon older and more crude humor.
James Madison, whose “My Old Kentucky Home”  has been chosen as showing clearly the elements peculiar to the burlesque tab, describes the difference in this way:
“Burlesque does not depend for success upon smoothly joined plot, musical numbers or pictorial effects. Neither does it depend upon lines. Making its appeal particularly to those who like their humor of the elemental kind, the burlesque tab often uses slap-stick comedy methods. Frankly acknowledging this, vaudeville burlesque nevertheless makes a clean appeal. It does not countenance either word or gesture that could offend. Since its purpose is to raise uproarious laughter, it does not take time to smooth the changes from one comedy bit to the next, but one bit follows another swiftly, with the frankly avowed purpose to amuse, and to amuse for the moment only. Finally, the burlesque tab comes to an end swiftly: it has made use of a plot merely for the purpose of stringing on comedy bits, and having come toward the close, it boldly states that fact, as it were, by a swift rearrangement of characters—and then ends.”
 See the Appendix
While the burlesque tab nearly always opens with an ensemble number, and almost invariably ends with an ensemble, there may be more solos, duets, trios, quartets and ensembles than are used by the musical comedy—if the act is designed to run for a longer time. But as its appeal is made by humor rather than by musical or pictorial effect, the burlesque tab places the emphasis on the humor. It does this by giving more time to comedy and by making its comedy more elemental, more uproarious.
In a burlesque tab, the comedy bits are never barred by age—providing they are sure-fire—and therefore they are sometimes reminiscent.  The effort to give them freshness and newness is to relate the happenings to different characters, and to introduce the bits in novel ways.