Jörg Widmann is a German composer who is acutely conscious but certainly not in awe of his musical forebears. His best-known string quartet, no. 3 ‘The Hunt’ makes dramatic use of – and has great fun with – Schumann. His 2011 concerto Flûte en suite, performed at the 2014 Proms, more than nods to Bach and baroque elegance. In Armonica, commissioned by the International Mozarteum Foundation to celebrate Mozart's 251st birthday in 2007, Widmann surprisingly and yet unsurprisingly features the glass harmonica, the distinctive instrument that Mozart featured in his own last chamber piece, the Adagio and Rondo for glass harmonica, flute, oboe, viola and cello, K617. Mozart teamed the instrument with the quieter representatives from the wind and string families; Widmann places it against the whole orchestra.

Armonica is an old term for the glass harmonica, but it also refers to the accordion, Zieh-Harmonika in German, and Widmann features this instrument too, finding in its quiet, breathy swellings and exhalations a bedfellow to the glass harmonica's unworldly ability to sustain chords. The two instruments not only complement one another, they give the lead to Widmann's orchestral writing and the whole character of the 15-minute piece. The emphasis on high-pitched sounds from metal percussion, harp, piano and the unique sound transformation of the water-gong certainly contribute to what Widmann calls ‘a musical suspension of gravity’. The piece is slow-paced throughout and divisi strings typically build chord on chord, but the work's title also suggests the idea of harmony itself, of the harmony of the spheres. The way a low plucked bass note triggers a kind of slow arpeggiated chain reaction among the orchestra, ending in glinting crotales, is a good example of the work's sensuality. Its otherworldliness could have been heightened by the use of electronics, but it is characteristic of Widmann's ability to enchant that the real coup lies not in exotic instruments but in the glass harmonica soloist's gentle wordless singing into her instrument at the end. Armonica resembles a kind of Daphnis and Chloe of our time; its rather French harmonies were created by the BBC Philharmonic under John Storgårds with Christa Schönfeldinger (glass harmonica) – discreetly amplified – and Teodoro Anzellotti (accordion).

Celestial harmonies also inspired the British composer Mark Simpson (b. 1988) whose 2014 orchestral work Israfel takes its title from the angel in Edgar Allan Poe eponymous poem, itself based on a passage in the Koran in which the angel is described as one ‘whose heart-strings are a lute, and who has the sweetest voice of all God's creatures’. Israfel was premiered by the BBC Scottish SO under Andrew Litton in 2015; at the Proms the BBC Philharmonic (with whom Simpson is now Composer in Association) gave the work a welcome second performance directed by Juanjo Mena. Mena also conducted the premiere of Simpson's biggest work to date, the superb The Immortal (2014) for baritone, choruses and orchestra. Similarly direct, sensual, powerful and instantly communicative without selling itself short, it deservedly won the 2016 South Bank Sky Arts Award.

At the 2015 premiere of Israfel David Kettle's review in The Times detected ‘Messiaen-meets-Scriabin harmonies’. In truth the work lacks the visionary/religious ecstasy of the Catholic Frenchman or the intense theosophic fervour of the latter, and this is to its advantage. Instead Simpson's sound world is grounded in the rhapsodic carnalities of Earth, just as Poe's Koranic angel was a cover for his take on fleshy decadence. Poe is a good resource for Simpson: ‘… this / Is a world of sweets and sours’ as ‘Israfel’ has it, nicely captures the atmosphere of the first half of this 12-minute work. The woodwinds have a memorable two-bar melody, often repeated, while at the same time stopped brass ‘sour’ the lyricism with some darkness. Impassioned strings keep Simpson's highly coloured music flowing dynamically and bass drum/glockenspiel thumps add a satisfyingly old-fashioned emphasis in a fashion reminiscent of late Rachmaninov. In the second half of this sensual feast, the drum and glockenspiels punctuate a progression of more and more strained chords that brings the ‘pulsate, quicken and increase-the-drama’ John Adams of the 1980s to mind. Israfel builds on the visceral excitement and physicality, and the delight in the orchestra, that Simpson showed as early as 2008 in A mirror-fragment, written when he was 19, but it adds a depth, a softness, that the early, somewhat brittle piece lacked. Simpson is currently working on a cello concerto to be premiered by the BBC Philharmonic and Mena with Leonard Elschenbroich as soloist, to be premiered in May 2017. Let's hope it cements his place as one of the leading younger British composers.

On the face of it, Emily Howard's (b. 1979) concerns couldn't be further from Mark Simpson's. Of the same generation of British composers and, like him, with one Proms performance already to her name (his sparks, hers Calculus of the Nervous System), Howard has her roots in science. Her first degree was in mathematics and her works often have mathematical inspiration and titles, not only Sphere, due to be premiered next year, and the continuing series Orbit, but also Torus which the Royal Liverpool PO under Vasily Petrenko premiered at the Proms. Howard has a long association with Liverpool, her home city; the new work for the RLPO is subtitled Concerto for Orchestra and lasts 20 minutes.

The form of Torus (mathematically a circle with a circular void at its centre) is described by Howard as ‘rotational’, by which she means that the strings provide a constant encircling frame while the wind, brass and percussion – often tuned microtonally – ebb and flow, quicken and slacken to interrupt the circle's perfection. ‘Perturbations’ was a word that Howard reached for in her pre-Prom talk and the perturbations increase in their agitation as the piece progresses and the metal percussion rings out alarmingly. The acceleration and slowing up sounds distinctly machine-like. The disturbances move from background to foreground, providing lively rhythmic patterns for brass and percussion particularly, before a brief coda where the concerto returns to its quiet, stable string harmonies.

Howard eschewed any descriptive references in speaking about the new piece. ‘I want to take scientific ideas and play with them’, was her characterisation of her approach but ‘it's sound that interests me’. Neither Torus – nor Magnetite (2007), her breakthrough work, now available on an NMC CD (NMCD219) – has a cool or affectless ‘scientific’ atmosphere. Nor does she compose to set mathematical schema like, say, Andrzej Panufnik. Howard's signature technique of creating drama – a rhythm repeated then modified, before further repetition – provides a clear way in for listeners and the NMC CD shows her approach in a number of orchestral pieces, together with a few for smaller ensembles. Magnetite sounds now like a precursor of Torus, a static, or slow-moving landscape dominated by strings over which high percussion glints, brass explode like colourful nebulae and dissolve, and the whole orchestra scuds forward propelled by a bass-drum thwack. For a more inward, edgier Howard, head for the works for small ensembles, where reduced resources prompt her to focus on extremes of timbres, minutiae of change and unsettling harmonies, Try both Afferance for string quartet and Threnos for two unaccompanied voices for more dangerous explorations into strange new worlds.