A solo record in every sense of the word, Müller wrote, recorded, arranged and produced Heliopause. The album is named after the boundary where the sun's wind ceases to have influence. It is ultimately, the border of our solar system. The name struck a chord with Müller since the two voyagers sent on an exploratory mission 42 years ago, recently crossed the Heliopause, entering into interstellar space and losing power from our own sun. Müller recognized herself in this moment, not only approaching the same age, but also breaking new ground; having relied on collaborating with so many other stars and now venturing into the unknown with her first solo statement; "Heliopause marks the end of a long journey but also the start of voyages to explore strange new worlds".

Boldly opening the album with "Being Anne", it sees Müller embrace her new found freedom with the most experimental piece on the record, placing the cello in a completely new context. Playing the strings of a broken down piano with a plectrum and scratching parts of the key mechanism to produce a rhythm, the once lost instrument is given a new lease of life among looped cello drones and drums.

"I used the sounds of a tiny piano I got from my mother that she bought when she was a student and didn't have any money. Later it stood for years in our little summer garden house, where I practiced on it constantly for my piano lessons. Even though it's old and not in the best shape, I love the way it sounds and call it my little circus piano".

The atmospheric swells of noise on Being Anne are juxtaposed beautifully with the most stripped back and exposed song, Solo? Repeat!. The J.S. Bach and Gaspar Cassadó influenced piece sees Müller go solo in its purest form: unaccompanied cello. Lead single Nummer 2 is so titled as it's the second piece Anne ever wrote. A mixture of old sounds and newer structures, its repeated arpeggio conjures drama and displays Müller's dexterous production abilities. Drifting Circles meanwhile provides the album's climax, amid an orchestra of looped cellos and vocals. Referencing the minimalism of contemporary composers such as Steve Reich and Philip Glass, it builds to a crescendo of harmonics, allowing the cello to sore as it crosses the border from minor to major.