The Flex-Ability series, arranged by Victor López, fills the need for multi-level instrumentalists to play popular music together. Each instrument book includes 11 songs in four-part score form. The top line (solo) is for level 2.5--3. The second line (duet/harmony) is for level 2--2.5. The third line (trio/harmony) is for level 1.5. The bottom line (harmony or bass line) is for level 0.5--1 (only whole, half, dotted half, and quarter notes and rests). The arrangements are carefully crafted to be educationally sound. Optional octaves and cue notes are included to allow for range flexibility