Solo guitar records seem to come out with alarming frequency these days. They have a markedly different flavour from solo saxophone records (so common in improvised music) or solo piano ones, the mainstay of the classical world.

Chuck Johnson's offering (oddly released under the name "Ivanovich") comes from the improv end of the spectrum, with a definite rock influence. The nineteen tracks on Solo Guitar are all very different, employing a range of techniques familiar to any avant guitarist: drumming on the strings, scraping, seeking out extreme harmonics, making percussive sounds and so on. Some tracks, such as the opening couple, feature just one technique and explore it in some depth.

The truth is that these pieces don't really make much impact. We've all heard these sounds before, and Johnson does little to string them together into musical structures. Indeed, it seems almost perverse for him to focus so closely on technique when he's not really a technically gifted player. His performance is often rather sloppy, leading to unexpected pingings or dead notes where they were surely unintended (or at least where they make no musical sense).

This lack of virtuosity shouldn't be off-putting, however. Johnson has bags of energy, which he employs in the straighter tracks like "z.h.r.," a clawhammer-picked piece which wavers between country-rock and weightless abstraction. He also has a likably swaggering delivery on "curved air," ostensibly a violin bow showcase but actually an incomprehensible anecdote-without-words which weaves drunkenly around a limited range to great effect.

Johnson is definitely better on electric guitar than acoustic, and what he lacks in technical wizardry he more than makes up for with attitude and timing. This is a pretty enjoyable disc, but probably not Johnson's best format. Perhaps he's something like Marc Ribot: great in bands, less good solo. This is patchy but very appetite-whetting stuff.

Paolo Angeli, on the other hand, seems to be come from a classical background. Linee di Fuga is a very different-sounding record from Johnson's Solo Guitar, although many of the same things are going on. One difference is Angeli's choice of instrument, the Sardinian guitar, which is a folk variation on the Spanish guitar and which Angeli further varies by means of preparations, extended techniques and a massive rack of effects.

It's astonishing that there are no overdubs here; Angeli's technique is of the nylon-pumping, macho speed-freak kind, and he makes several things happen at once with that atavistic attraction to difficulty for its own sake which guitarists seem stricken by. He sounds like an atonal, grating Adrian Legg.

One problem with all this is that Angeli seems to have an uncertain grasp on how to make sense of a stretch of musical time. He switches from one astonishing gymnastic display to another with little real logic. Yes, it's extremely impressive, but pieces like the title track, which switches arbitrarily between punchy straight picking and bowed orchestra-isms, can be extremely frustrating as well.

The switches in this piece, incidentally, are studio edits, not live transitions (which would surely prove impossible even for Angeli). The CD documents a mixture of improvisations and compositions (including two traditional pieces) and a combination of live playing and studio work.

Like Johnson, Angeli is probably at his most effective and at his most comfortable when he abandons the necessity to show off "new" sounds and just plays relatively straight. Then he sounds a little like Robert Fripp, mixing a strong rhythmic pulse with jagged, semi-tonal lines. Indeed, pieces like "Piano a Denti Stretti" could easily be vintage King Crimson compositions.

Looked at pessimistically, this is a failed semi-classical guitar record with dreadfully misjudged avant pretensions. But looked at another way, it's a pretty satisfying prog rock disc; there are a lot of much, much, much worse virtuosic guitar albums out there and this one will give you hours of pleasure if this kind of thing is your bag. Fripp fans are encouraged to seek it out and not be put off by the title track; others approach with more caution.