Since their launch in 2002, the Glasgow Improvisers Orchestra (GIO) have steadily refined the delicate balance of big-line-up free-improv and arms-length navigation – in the process attracting new-music solo luminaries of the stature of saxophonist Evan Parker and pianist Marilyn Crispell, who are respectively the principal soloists on these two BBC-sponsored live recordings. The two gigs are alternative versions of the same composition – saxophonist Raymond MacDonald's ‘Parallel Moments Unbroken’, a combination of regular notation, graphic scores, and visuals designed to massage moods and vary textures without laying down the law. Both shows have their share of free-jazz tumult, but interlaced with deep brass undertows to solo lines reminiscent of Gil Evans or Carla Bley, eerie lost-ghost vocals, and – naturally – passages of dizzying inventiveness from Crispell on the December 2013 gig and Parker the following June. Crispell shifts from wide-spaced sounds and deep reverberations to darting clusters and onrushing Cecil Taylor-esque chordwork on the solo feature ‘Parallel Signs (e)’ while Parker turns it into a seamless tenor cascade of circling, seesawing whoops and overlapping lines. ‘Parallel Melbourne’ mixes coaxing trombone calls and trancelike hums on version one, and turns from firm, explicitly jazzy muted trumpet figures to scurrying collective jamming on two. ‘Parallel Moments’ (a piano/sax duet) features Parker in a low and lustrous deep-tenor murmur on his version, while Crispell's account with tenorist Graeme Wilson shifts from call-and-response to a neck-and-neck gallop. The comparisons are fascinating, on an ambitious improv/compositional venture full of surprises, virtuosity, lyrical understatement, and uncompromising energy.