Donny McCaslin and Miles Mosley make for memorable Istanbul Jazz Festival

Though there's no overt political message (I'm told one lyric is about this life's unavoidable tears, and the salve of the afterlife to come – more gospel than rebel rock in sentiment), Futaci's Kara Orchestra play ritual, Near Eastern jazz-rock with an unmistakable underground edge. They fade in and out of focus in a dislocating, mantric haze, Futaci's tenor sax facing off with Bariş Ertürk's baritone, as psychedelia, muscular free jazz and obscure invocations pass through local, ancient filters. What's happening feels committed, rooted and urgent. In nearly a week in Turkey's vast capital, nothing quite matches it.

Istanbul Jazz Festival includes a strong international line-up (Antonio Sanchez, Dee Dee Bridgewater, Donny McCaslin (top), Joshua Redman, Christian McBride and Roberto Fonseca among them). My stay, though, is based around ViTRin, its Turkish new music showcase. In a former shoe factory's gardens on the Bosphorus's banks, MadenÖktemErsönmez further update the legend of Turkey's 1970s underground rock. Playing in front of dark stripes of scaffolding resembling a Tudor house in the moonlight, guitarist Sarp Maden sparks feedback from a fast, bucking solo. The bright laser buzz of his instrument has a vintage science-fiction sheen, amidst a simmer of rattling beats, finger-popping bass funk and spectral atmospherics. Someone approvingly mentions Can. Before them, Miles Mosley & The West Coast Get Down (below) brew up a quiet storm with Hendrix's 'If 6 Was 9'.

Then there's Junun (below), who on their self-titled album were a collaboration between Radiohead's Jonny Greenwood, Israeli singer-guitarist-flautist Shye Ben Tzur and India's Rajasthan Express. Greenwood's back at his day-job, but Ben Tzur is this heavy, highly danceable Qawwali trance and swing's guiding force. With a band drawn from Tel Aviv and a Sufi Muslim saint's shrine, and Ben Tzur's composition of devotional Qawwalis in Hebrew, when he thanks God, he is melting religious divides. Such projects can sound trite, but this music's potent existence moves me to tears. It's the philosophy behind Istanbul's grand Hagia Sophia museum, with its exposed layers of Christian, Muslim and secular history, of Byzantium and Constantinople.

Crossing the Bosphorus to its Asian side's bohemian Moda neighbourhood for a multi-venue 'Night Out', Gevende are the highlight, influenced by Radiohead, but as individual as their lyrics' polyglot, imaginary language. A bereft trumpet intertwines with rippling guitar on a softly crooned ballad. Finally, jagged wah-wah guitar is displaced by Bootsy Collins rubber-band bass, and Miles electric funk. Turkish indie-rock in theory, Gevende are on their own trip. Though my chosen musical route-march misses them, colleagues also enjoy Kolektif Istanbul's "progressive wedding music", a Balkan-Anatolian blend suiting this crossroads city.

At a concert down amidst the millennia-smoothed Byzantine columns and fearfully inverted Medusa heads of Yerebatan Cistern, Özer Arkun's cello and Fatih Ahiskali's oud duet with a melancholy familiar from here to Europe's old gypsy and Jewish ghettos. At the French Consulate's Palais de France gardens, meanwhile, pianist Can Çankaya and bassist Kağan Yildiz play stately hard bop in the early moonlight, harmonising for a moment with a nearby call to prayer. Unremarkable in style, they feel cleansing tonight. The straight Turkish jazz I hear is often disappointing, trying hybrids which just miss the mark (though I'd like to have heard more of the acoustic, Anatolian Bilal Karaman Trio). A panel of local music business veterans speaks realistically of hard times, greeted by knowing gallows humour from the audience.

Looking out at the Bosphorus one night, I run into a musician who mentions the frustrations of being an artist here, unable to say what he'd like. The situation with President Erdogan is otherwise left implicit, and never volunteered (though a massive, defiant protest march reaches Istanbul from Ankara as I leave). This oppression at the city's edges is something I considered before travelling, but I'm profoundly glad I came. Istanbul makes London look small and young, and offered the nuances of cosmopolitan conversation, human generosity and sometimes subtly brave, enlivening music. People are bigger than their governments.

– Nick Hasted
– Photos by Mahmut Ceylan and Faith Kucuk