At six, he began music lessons and at seven, took up the piano. In the 1980's he was not accepted into the Music Academy of Bratislava because his concept of music, at that time, was heavily influenced by the Western avant-garde. At 27, Machajdík graduated from the University of Economics in Bratislava.
Peter Machajdík first became internationally recognised after the success of his multi media work Intimate Music featuring David Moss at Inventionen 1994 in Berlin. His prolific output has since been performed and broadcast around the world, placing him in the front rank of today’s composers. His major works include Double Bayan Concerto, Nell'autunno del suo abbraccio insonne for Italian harpist Floraleda Sacchi, Nájdené zabudnuté for orchestra, and Namah 'for peace on earth' for string orchestra which was premiered by conductor Anu Tali at the Concert Hall of the Slovak Radio Bratislava in 2002, and was also a featured work at both the Epoche and Divertimento Musicale festivals in 2006. The CD Namah with guest appearances such as Jon Anderson of Yes, Floraleda Sacchi, David Moss, Guido Arbonelli and others was released on musica slovaca label in October 2008.
Machajdík has received numerous commissions and awards from, among others, the Kulturfonds Foundation, Russolo-Pratella Foundation, Slovak Music Fund, Czech Radio, German Accordion Society, Bratislava Music Festival, and International Visegrad Fund. In 1992 he was invited to live and work in Berlin as a guest of the prestigious DAAD Künstlerprogramm. Machajdík was also the artist in residence at Schloss Wiepersdorf, Germany, at Künstlerhäuser Worpswede, Germany, and at Künstlerhaus Lukas in Ahrenshoop on the German Baltic coast. In 2006 he was awarded the Jan Levoslav Bella Prize, the most significant classical music award in Slovakia.
Since 1985, Machajdík's works have been performed and exhibited at numerous performance spaces, museums, galleries, and festivals, including Inventionen, Berlin; New Work Festival, Calgary; Hörgänge, Vienna; young.euro.classic, Berlin; Nuovi Spazi Musicali, Rome; Melos-Ethos, Bratislava; Kunstforum Ostdeutsche Galerie, Regensburg; 5 Giornate per la Nuova Musica, Milano; Festival de Jazz et Musiques d'Aujourd'hui, Mulhouse; Kunstverein Wien, Vienna; Bremer Kunstfrühling, Bremen; Review of Composers, Belgrade; Audio Art Festival, Cracow, as well as in the Netherlands, Belgium, Canada, Switzerland, Denmark, Portugal, Uruguay, the Czech and Slovak Republics, the United Arab Emirates, and the U.S.A. Some of the venues where his compositions have received their first performances include Deutsche Oper Berlin, Slovak Philharmonic Hall Bratislava, Konzerthaus Berlin, Tenri Cultural Institute New York, Ignacy Paderewski Pomeranian Philharmonic Hall, Adolphus Busch Hall Cambridge (MA), and Sala Filarmonica in Trento. Performers of Machajdík's music have included artists such as David Moss, Floraleda Sacchi, Carson Cooman, Elina Mustonen, Guido Arbonelli, Rocco Anthony Jerry, Boris Lenko, Milan Paľa, Natalia Pshenichnikova, Mayuko Kida, Piet Van Bockstal, conductors Anu Tali, Miran Vaupotić, Peter Breiner, Maria Makraki, Marián Lejava, Ondřej Kukal, Aleksander Gref and Karol Kevický, the Janáček Philharmonic Orchestra, the State Philharmonic Orchestra of Košice, ARTE Quartett, Slovak Chamber Orchestra, AccoDuo, Camerata Europea, Lugansk Symphony Orchestra, Ignacy Jan Paderewski Pomeranian Philharmonic, Quasars Ensemble, Veni Ensemble, Zwiebel Quartet, Slovenian Clarinet Quartet, and many others.
Machajdík has also worked and performed with Jon Rose, Nicolas Collins, Dietmar Diesner, Transmusic comp., Malcolm Goldstein, Tom Guralnick, Peter Hollinger, Heiner Goebbels, Martin Burlas, Luc Houtkamp, and many others.
Machajdík's interest in other performing arts and in collaborations led him to compose numerous works for film, theatre, modern dance companies and visual artists. He was co-founder of the Transmusic comp., which introduced mixed-media, free improvisation and performance work in former Czechoslovakia. In the late 1970s and early 1980s he had smuggled some of his compositions to the famous American minimalist duo George Cup & Steve Elliott, who used his music in their video works.
Machajdík has lectured on new music and sound art, led workshops, and curated festivals of contemporary music and multimedia art such as Sound City Days 2012 in Košice. His music has been broadcast many times on radio and TV all over the world. Machajdík scored films such as 'Altenburg - Vier Schüler gegen Stalin' by Hanno Brühl, 'Návrat rysov' (Miloš and the Lynxes), 'Cesty Slovenskom' (Accross Slovakia) by Tomáš Hulík, and others.
Machajdík often chooses to compose his works in solitary places. His compositions draw on several sources of inspiration, especially from the polyphony and modal harmonies of early music. In recent years Machajdík's works have been typified by both economy of material and stringency of method, thereby demonstrating that what may be simple musical language can nevertheless be powerful. Also elements such as controlled use of dissonance, sustained sonorities, inconspicuous melodic motion and frequent use of minor tonalities apply to Machajdík's compositional style. Most of his compositions have a meditative character.
- THE IMMANENT VELVET, CD © 2012 R266 0024-2-331
- TYPORNAMENTO, CD © 2012 Guerilla Records 080-2
- A MARVELOUS LOVE (Carson Cooman - organ), CD © 2012 Albany Records TROY1357
- VIOLIN SOLO (Milan Paľa), Vol. 4, CD © 2012 Pavlik Records PA 0098-2/9
- CZECHOSLOVAK CHAMBER DUO, CD © 2012 CR0591-2
- INSIDE THE TREE, CD © 2011 AA 11003
- VIOLIN SOLO (Milan Paľa), Vol. 3, CD © 2011 Pavlik Records PA0092-2/9
- MINIMAL HARP (Floraleda Sacchi), CD © 2009 Universal/Decca 476 3856
- NAMAH, CD © 2008 musica slovaca SF 00542131
- R(A)DIO(CUSTICA) SELECTED 2008, CD © 2008 Czech Radio
- NUOVE MUSICE PER TROMBA 6 (Ivano Ascari), CD © 2088 AZ 5005
- NAMASTE SUITE (Guido Arbonelli), CD © 2003 Mnemes HCD 102
- THE RÈR QUARTERLY, CD © QUARTERLY, ReR Volume 4 No 1 CD - ReR 0401
- POŽON SENTIMENTÁL, CD © 2000 musica slovaca SF 00252131
- Official CD-Shop 
Recent interviews with Machajdík
- Oliver Rehák, "Peter Machajdík: Vždy unikám z toho, k čomu kráča väčšina", Hudobný život 3, 2009. (Slovak)
- Zuzana Kizáková, "Peter Machajdík: Netvorím duchovnú hudbu. Ale hľadám zmysel", Pravda 18 November, 2009. (Slovak)
- Petr Slabý, "Peter Machajdík: Baví mě skládat svobodně bez jakýchkoliv témat", UNI 8, 2011. (Czech)
- Kamil Zbruž, "Peter Machajdík: S Karlheinzom Stockhausenom sa stretávam na hviezde Sírius", Kloaka 3, 2011. (Slovak)