In contrast to the Swamp Sparrow (Melospiza georgiana) and Song Sparrow (M. melodia), vocal studies of the congeneric Lincoln's Sparrow (M. lincolnii) are essentially lacking. To provide comparative data on song variation in this species, we obtained and analyzed recordings from 58 males (4,537 songs) breeding in montane meadows of the Sierra Nevada and San Bernardino Mountains, California. Males sang from one to six song types, and repertoire size averaged 3.7 types. No two males shared an identical song type. Males varied their types by changing the number of repetitions of a syllable or by adding, deleting, or substituting one or more syllables (i.e. by changing syllable composition). The number of variants, identified on the basis of differences in syllable composition, averaged 2.6 per song type (range 1 to 12). Individual variability was highest in the terminal elements of the song. Production of variants appears to be a process of “open-ended improvisation” of song types. Similarity of songs on the basis of shared syllables, as calculated by simple matching coefficients, showed a strong pattern of concordance with geography. Pairwise similarity declined with increasing distance between meadows, and meadows from different geographic regions clustered separately in a UPGMA tree. Patterns of geographic variation in song of Lincoln's Sparrows are similar to those observed in Song Sparrows and Swamp Sparrows. Song complexity and repertoire size show different evolutionary trends within Melospiza.