Listening to Madlib's Beat Konducta series is a bit like going to a soul-music fetishist's peep-show and having the shutter slam down unceremoniously on your cock every couple of minutes. It's quite a frustrating experience but not an entirely unpleasant one... if you're into that sort of thing.

The fifth and sixth instalments of the Stones Throw series, Vol. 5:Dil Cosby Suite and Vol. 6: Dil Withers Suite (available together on CD or as separate LPs) once again compile a crazy amount of tantalisingly short instrumentals: only a handful break the three minute barrier. These quick sketches of beats barely have time to get going before they are cross-faded into the next or abruptly interrupted with a vocal sample.

It's essentially a beat tape - a collection of raw material for beats which producers hand out to their peers and collaborators. This is probably exactly the sort of thing you'd hear if you showed up at the Neptunes' studio back in the day with a suitcase full of money looking for a guaranteed chart topper. Pharrell (and the other one) would probably offer up a selection of yet-unclaimed drum fills, synth lines and falsetto vocal riffs ready to be chopped up, pitch shifted and crafted into a bespoke beat to make any emcee sound good - so long as Pharrell got to sing the chorus.

The story goes that, in the early days, 'Beat Konducta' was what Madlib wrote on his coveted tapes full of nascent backing tracks that he passed out to friends. The Beat Konducta series is an approximation of these rare documents, mixed together, smartly packaged and sold to you, the discerning record buyer. So why would you, the discerning record buyer, want a bunch of truncated tracks instead of full ones and why, for that matter, would Madlib release his B-material to the public?

Naturally, if you're a DJ you can make good use of these tracks as transitions, but I think the average bedroom listener has something to gain as well. While the style and sounds are all over the place there does seem to be a unified tone to the piece. It's quite similar in feel to another collection of song sketches - the very rare A Few Old Tunes bootleg by Boards of Canada - which also began as a gift to friends and family and is also composed of partial tracks, some less than 30 seconds long. These fleeting little songs pass like fragmented memories in your head, eroded by years of reverb. Similarly, Beat Konducta Vols. 5 & 6, with their often naked samples, not overly produced or buried, give you the feeling of listening to the radio through a tear in space-time. Also both sections make excellent use of short and evocative Brian Enoesque titles to ground the experiments with visual imagery. This sketchiness lends to a naturally spacey, dreamy quality, a unique listening experience.

One has to appreciate Madlib's commitment to sifting through vinyl because some of the samples are stunning even without much manipulation. There's plenty of his trademark chopping up and rearranging soul samples, playing back the notes like an instrument, but some of the best tracks come from surprising sources: the Buzzcock's 'Boredom' is effortlessly turned into a track to make Rick Ruben jealous on 'The Get Over (Move)'; 'Dirty Hop (The Shuffle)' makes Throbbing Gristle's ‘Convincing People’ both sexier and more threatening. Tracks like 'The Electric Zone (Plugged In)' are more concepts than songs but are equally interesting for the thought process.

While volumes one and two were ostensibly movie soundtracks and three and four composed entirely of 70s and 80s Bollywood film samples, there is no unifying concept here. It is instead a tribute to his friend and collaborator J Dilla, who died in 2006. At the end of his life, Dilla famously leaked beats much like these through file sharing programmes, which was no doubt the inspiration for the series. When you consider that Madlib is, in way, consigning these tracks, any number of which could have been developed into killer singles, to a two minute purgatory, it's actually a very touching idea. It's as if to say, 'these beats are for J Dilla; no one else can have them'. It’s certainly a far less cheesy way of pouring a 40 on the curb.

Anyway you look at it, Beat Konducta Vols. 5 & 6 feels special, a very personal album, like something you stumbled on that only a select few are supposed to have heard. Despite the inherent frustration it's a rewarding listen, if you have the patience, and I'm sure J Dilla would find it a fitting tribute.