Altstaedt was born in 1982 in Heidelberg, West Germany. In 1996, he enrolled at the Hochschule für Musik in Detmold, studying with Marcio Carneiro. He moved on to the City of Basel Music Academy and rounded out his education at the Academy of Music "Hanns Eisler" in Berlin, where his teachers included Boris Pergamenschikow; he was one of the great cellist's last students. Several major prizes between 2003 and 2010 propelled Altstaedt's career forward, including those at the Concours d'Interpretation Musicale Internationale in Lausanne, the International Domnick Cello Competition of New Music in Stuttgart, and the Adam International Cello Competition in New Zealand. He performed with the Vienna Philharmonic under conductor Gustavo Dudamel at the Lucerne Festival in Switzerland in 2010, and from 2010 to 2012, he was a BBC New Generation Artist. Altstaedt has appeared in many countries, with such ensembles as the Tonhalle Orchestra in Switzerland, the Czech Philharmonic, and the Tokyo Metropolitan Symphony Orchestra, as well all the BBC symphony orchestras. He has given recitals at such prestigious venues as BOZAR in Brussels, Carnegie Hall in New York, and the Théâtre des Champs Elysées in Paris. Altstaedt's chamber music partners are a distinguished group, including violinists Janine Jansen and Vilde Frang, as well as the Quatuor Ebène.
Altstaedt has made more than a dozen recordings, the first being an album of French cello sonatas on the Naxos label. He has gone on to record for Genuin, Channel Classics, and Hyperion, among other labels, and in 2020, he joined fortepianist Alexander Lonquich on the Alpha label for a recording of Beethoven's complete works for cello and piano. Altstaedt moved to the BIS label the following year, issuing an album of works for cello and piano by composer Sebastian Fagerlund with the Finnish Radio Symphony Orchestra under conductor Hannu Lintu. ~ James Manheim, Rovi