Like the dashes between the above letters, microtones lurk between the notes we're used to hearing in music. Actually, we hear microtones—sometimes characterized as "the notes between the notes"—all the time. When a guitarist bends a string or a warbling singer swoops back to the melody, we listen to notes that are not part of the 12-note-per-octave scale that is the tonal template for popular music, jazz, classical, and much of the avant-garde.

Makers of microtonal music, including those performing at the Seattle Microtonal Guitar Festival (SMGF), seek to take those "notes between the notes" beyond the role of an expressive device and make microtones the substance of music itself.

Composer Tom Baker, whose improvising quartet opens the SMGF, says that "playing microtones taught me to work with and weigh intervals of different sizes." Baker's quartet shares the bill with the Stone Crazy Blues Band, which features guest guitarist Jon Catler, a veteran of legendary composer La Monte Young's Forever Bad Blues Band. Speaking by telephone from New York, Catler discussed working with a 62-note-per-octave scale on a specially fretted guitar. "This scale is nature's gift to us." And that given the ongoing evolution of tuning systems, "the history of music is people learning to hear the higher members of the harmonic series."

The four-day festival encompasses performance/demonstrations (Fri July 21, Gallery 1412, 8 pm), a concert with Catler and Neil Haverstick (Sat July 22, Brechemin Auditorium, 8 pm), and a concluding workshop led by Catler (Sun July 23, Roberts Institute in Bellevue, 2 pm). For more information, see www.microtonalguitar.com.

The Seattle Microtonal Guitar Festival begins with the Tom Baker Quartet and the Stone Crazy Blues Band on Thurs July 20 at Lo_Fi, 429B Eastlake Ave E, 323-8853, 9:30 pm, $7.