Giving themselves new challenges, two of France’s most accomplished double bass players are involved in duos that stretch the definition of improvisation.

Expanding her sound philosophy that encompasses so-called modern classical music as well as improv, Joëlle Léandre has recorded 14 miniatures with Gianni Lenoici, a pianist from Monopoli, Italy, who has a similar background to hers. Speaking of background, Claude Tchamitchian, usually found in the company of hard-core improvisers such as pianist Sophia Domancich, guitarist Raymond Boni and reedist Daunik Lazro, here taps into his Armenian roots, improvising with kamancha master Gaguik Mouradian.

Usually fashioned with two or three strings, but here with four, the kamancha is about the size of a small banjo, is held vertically resting on a pike, and is played with a bow like a cello. Mouradian, who has lived in France since 2000, is a teacher and traditional kamancha player, respected enough to make concert appearances as a soloist with the (Armenian) National Ensembles of Song and Dance. Adapting his Middle Eastern-oriented instrument to freer music, he has played with Tchamitchian for a decade, as well as with other improvisers such as Boni and American saxist Joe McPhee.

A forceful player, Le monde est une fenêtre (the world is a window) finds the kamanchaist duetting with the bassist on 15 tracks divided into groups entitled “Voix”, “Visions”, “Visages”, “Rivages”, “Regards” and a final “Rêve”. Here Mouradian’s command of mughams, a Middle Eastern modal system, melds and rebound off the pizzicato and arco styling of Tchamitchian, whose experience encompasses work with choreographers, electroacoustians and so-called classical musicians as well as improvisers.

Oddly enough, when the two Europeans get into full string band mode suggestions of American Old-Timey sounds appear as well. After all, with 70% of Armenia’s terrain mountainous, it obvious there’s much more mountain music there than in Appalachia. Utilizing Persian inflections from the style of the ashoughs or Armenian troubadours, Mouradian’s playing is at times both polyphonically otherworldly and liltingly medieval.

You can hear this as early as the first track when his swelling sounds subdivide into multi-string, oscillating timbres. More sonorous, Tchamitchian forcefully pulls on and plucks at his strings and by the second and third tracks expand his palate with a dark, buzzing arco, which perfectly intersects with the fiddler’s bowed, contrapuntal, yet somehow homey, melody making.

Paced with spaced broken counterpart, the two conjure up distinct sound images. The final track, for instance, has all the trappings of a through-composed recital piece with established harmonies and the jettes played just so. Other times, as on “Visages Part 1”, Mouradian’s vibrating nodes suggest a brace of violins, while Tchamitchian’s ponticello bowing with a pronounced tremolo becomes so abstract and vociferous that at points he seems to riffing on his bass’s belly and ribs.

On “Rivages Part 1”, as Tchamitchian double stops, Mouradian’s bowing takes its distinctive Eurasian melancholy further to the east, arriving at a pensive timbre that resembles that of the four-string Mongolian sihu. As staccato asides become more diffuse, he makes common cause with the bull fiddler and the two construct the equivalent of a Cossack string orchestra out of four low-pitched and four high-pitched strings.

A forceful, inventive improviser in many circumstances, Tchamitchian’s adoption of new textures not only takes in European-style double and triple stopping, shuffle bowing and col legno techniques, but others that radiate elsewhere.

On one tune you could swear he’s playing an electric bass guitar. On another his axe of choice could be a santur or Armenian zither whose strings are struck with small sticks. From spaces near the tuning pegs he manages to produce flute-like whistles as well as disconnected jagged swipes from around the bridge. “Regards Part 1” showcases simple string slaps, midway between the styles of Charles Mingus and Pops Foster. These become perfect complements to Mouradian’s ethereal fiddle overtones.

Not clichéd world music, but multi-cultural improvisation, Le monde’s one drawback is the number and length of its tracks. Fewer, longer ones would have given more scope to the achievement here.

That’s perhaps the only drawback to Sur une balançoire as well. Fourteen tracks, ranging in length from slightly more than 90 seconds to less than five minutes really makes you yearn for more expansive interface between the two. Léandre, for one, is an old hand in this format, having recorded bass-piano duos with, among others, American Eric Watson, Japanese Kumi Wakao and Ryoji Hojito as well as Lenoici’s countryman Giorgio Occhipinti.

Lenoici, who teaches at the Nino Rota conservatory and also plays in reedist Eugenio Colombo’s jazz quartet, brings a non-idiomatic approach to his work here, including preparing his piano. On “balançoire 12”, for example, Lenoici responds with occasional, internal flat-picking with driving broken octaves to counter Léandre’s stretched lines, sudden ponticello swipes and sharp, resonating shuffle bowing. But who creates the pitched dobro-like string lines at the end? Is it Léandre or Lenoici?

The situation is clearer on tracks like “balançoire 5”, where the bass textures are initially shrill and harshly high-pitched, while the pianist outputs high intensity, romantic cadenzas and circular arpeggios, pitched forward, as if he was playing 19th century Russian music. As the bass turns to arco sweeps, Lenoici introduces a walking bass pattern himself, but still playing prettily as Léandre’s shuffled, extended cadences double and triple in pressure.

Lenoici’s output isn’t all recital delicacy however. At points he confronts the bassist’s whistling ponticello with strident, internal string sweeps. Furthermore, on “balançoire 2”, “balançoire 3” and “balançoire 4” he meets successive four-string challenges head on. Pedal-emphasized, high-intensity, dark voicing intersects with spunky, squeaky bass abrasions and clipped key accents, then expansive broken chords face extended thumps and walking bass lines. Eventually these twists and turns build up portamento, to Lenoici’s exploration of internal string preparations and stops that meet wood and string-stretching efforts from the bassist.

Léandre who sporadically accompanies herself verbally with staccato nonsense syllables, mostly confines her singing to her fingers, producing aviary-like string cries with analogous facility that she emphasizes recital-like counterpoint. Yet generally her double-bass facility is met by appropriate pianisms from Lenoici, whether they’re low- intensity clinking timbres that could come from a music box or pedal-powered tremolo.

Une balançoire is a seesaw in French, but only rarely in this commensurately balanced duet does the sound tilt in favor of one or another musician — and the same can be said of the other CD.