Several scholars have argued that iambic pentameter has been so important in the history of English poetry by contrasting it with the one other important meter (tetrameter), variously called "four-beat," "strong-stress," "native meter," or "four-by-four meter."</ref> Four-beat, with four beats to a line, is the meter of nursery rhymes, children's jump-rope and counting-out rhymes, folk songs and ballads, marching cadence calls, and a good deal of art poetry. It has been described by Attridge as based on doubling: two beats to each half line, two half lines to a line, two pairs of lines to a stanza. The metrical stresses alternate between light and heavy. It is a heavily regular beat that produces something like a repeated tune in the performing voice, and is, indeed, close to song. Because of its odd number of metrical beats, iambic pentameter, as Attridge says, does not impose itself on the natural rhythm of spoken language. Thus iambic pentameter frees intonation from the repetitiveness of four-beat and allows instead the varied intonations of significant speech to be heard. Pace can be varied in iambic pentameter, as it cannot in four-beat, as Alexander Pope demonstrated in his "An Essay on Criticism":