The Sun Ra Arkestra have long had a well-earned reputation as one of the hardest working bands in the music business. This tradition is kept admirably alive by its current leader, 90-year-old Marshall Allen, who has helped celebrate Sun Ra's centenary with a gruelling 46-date tour, taking in Australia, Japan, Croatia, Switzerland, set to end in Canada in September. Currently halfway through their itinerary, the band follow their Barbican appearance on May 31 with two nights at Cafe Oto - undeniably the best place in the UK to see them due to the intimacy and intensity of hearing a big band in such a small venue.

The first night was as thrilling as ever, with long-term members Allen (joining in 1958), Charles Davis (1955) and Danny Ray Thompson (1967), playing alongside the likes of Knoel Scott and Vincent Chancey (whose memberships date back to the mid and late 70s respectively) and newer members like the incredible Farrid Barron on piano and newest recruit Tara Middleton on vocals.

Highlights are too frequent to detail in their entirety but 'Somebody Else's World' (from 1970's My Brother The Wind) and Allen's version of Coleman Hawkins' slightly creepy, yet compellingly strut-worthy big band tune 'Queer Notions' really are something else. For the second night, the band are joined by a slightly nervous-looking Shabaka Hutchings, which suddenly makes sense of what I had heard the night before about a four-hour rehearsal taking place that day at The Vortex. Hutchings, who has been invited to join the Arkestra ahead of their recording session for BBC Radio 3 the following day, makes a fantastic addition to the band's sound, clearly earning the other musician's respect following a blistering tenor sax solo on 'Dancing Shadows', which initiates the second set.

More incredible still is the incendiary alto sax solo that Marshall Allen lets rip with in response to Shabaka's, leaving a literally dumbstruck expression on the younger musician's face that's truly heartwarming to witness. A riotous version of 'I'm Gonna Unmask The Batman', propelled by a truly preposterous amount of swing and swagger, and featuring fantastically gritty backing vocals by Marshall Allen, largely renders a pre-gig discussion about whether the band are avant-garde or pure entertainment somewhat irrelevant in the wake of this euphoric blues/big-band juggernaut. Even after such dizzying heights, the intensity scarcely lets up as the set progresses with Hutchings adding clarinet and bass clarinet as well as sax, taking the performance just past midnight for the second night running. Allen looks utterly exhausted as he leaves the stage but then, as I remark to the person sat beside me, I'm worn out myself just from watching them for almost three hours despite being half his age and having been sat down the entire time.

The next day, I drop into a studio in North London to watch the Arkestra at work recording ten tracks, due to be broadcast on Jazz on 3 on Monday June 30 at 11 pm on BBC Radio 3. Presenter Jez Nelson and I discuss the inherently chaotic element of their live shows, a hugely important aspect as far as I'm concerned in enabling the band to play the same tune differently from night to night. He's entirely right though in his belief that although there are some excellent live recordings out there (including the entirety of their recent performance at Primavera, Barcelona) not enough high quality studio recordings of Allen's version of the band exist. Whilst the sound engineer seems initially a little thrown by the ad hoc nature of the band's organisation, and the band themselves have to work to establish the kind of spontaneity they always exhibit during their live performances, eventually everything starts to fall into place. Versions of 'Queer Notions' and 'Saturn' scintillate like the sparkling lights cast in reflection from the band's glistening outer space outfits. 'Dancing Shadows' recaptures some of the magic between Hutchings and Allen from the night before. Guitarist Dave Hotep adds surprisingly synth-like textures to 'Love In Outer Space' and there are moments throughout the day when the combined prowess of Farrid Barron on piano and Allen on EVI (electronic valve instrument) really express the spiritual essence of Sun Ra's playing despite his physical absence.

The band have a wake-up call for around 5 am the next day, when they fly to Kamnik in Slovenia to play Veronica's Tales Jazz Festival, but I continue my personal centenary celebration by tuning into Jez Nelson's half-hour radio documentary, 'Travelling the Spaceways: The Cult of Sun Ra', at 11.30 on Radio 4. Recounting his original interview with Sun Ra from 1990, Nelson offers a succinct and moving personal account of how Ra's music affected him deeply, so much so that his first live encounter caused him to momentarily flee during Allen's early solo, which had caused him to perceive an intense blue light emanating from his alto sax. Some interesting discussion as to what exactly Ra meant when he claimed to be an angel is given a playfully humorous slant when a recording of Ra himself declares: "...but I've been promoted to archangel recently". Gilles Peterson discusses the enormously far-reaching influence Ra has had on other artists, John Sinclair talks about putting the Arkestra on at the Ann Arbor Blues and Jazz festival in 1972, where the band received a rapturous response from the 12,000-strong audience and Allen reveals that he currently works from a songbook of literally thousands of songs, some of which are still to be recorded or even heard by the public. Gilles Peterson continues the spirit of the centenary celebration with a three hour Sun Ra Special on BBC 6Music this Saturday from 3pm, which also promises to feature two tracks from the recording session as a taster ahead of the full broadcast on June 30.

The Arkestra return to sold-out Cafe Oto shows next Wednesday and Thursday, June 25 and 26, after dates in Croatia and France, and also play Glastonbury on the West Holts stage at 4 pm on Friday 27 June. A new three CD box-set, Sun Ra - Live In Nickelsdorf 1984, has just been released on Trost