McLachlan is the son of the writer Leland Bardwell, and studies at the Dublin Institute of Technology (DIT) Conservatory of Music and Drama (1982–86), the Royal Irish Academy of Music (1989–97), and Trinity College Dublin (BA 1988). He studies composition with William York, Robert Hanson and Kevin Volans. He holds a Ph.D. in musicology from Trinity College (1999) for a study of the relationship between analysis and compositional technique in the post-war avant-garde.
McLachlan is the featured composer in the RTÉ National Symphony Orchestra‘s “Horizons” series in 2003 and 2008. He also represents Ireland at international festivals, including the ISCM World Music Days in Slovenia in 2003 and Croatia in 2005. In 2006, his work Grand Action is commissioned as a test-piece for the AXA Dublin International Piano Competition.
McLachlan’s musical aesthetic is largely shaped by a desire to impart a sense of narrative and expectation to his music without recourse to pastiche rhetorical devices. A critic writes of a recording of McLachlan’s piano piece Nine: “The style of each little piece sends one’s imagination and musical memory reeling, some of them evoking French Impressionism, some jazzy in feel, some reminiscent of the miniatures for piano of Webern, and none of them in any way, shape or form derivative.” Much of his music is structured in contrasting and suddenly changing block-like sections of homogeneous material. The material within these sections is propelled by a rigorous focus on subtle rhythmic and melodic permutations, which result in both surface opacity and gradually increasing tension.
McLachlan’s works have been performed in the United States, Peru, Japan, South Africa, Britain, France, Italy, Germany, Holland, Switzerland, Finland, Denmark, Portugal, Spain, Romania, Moldova, Slovenia, Croatia, and around Ireland, with broadcasts in several of these countries. Performers who have played his music include the National Symphony Orchestra of Ireland, Opera Theatre Company, the National Chamber Choir, Concorde, Sequenza, Traject, Archaeus, the Pro Arte Orchestra, Antipodes, Ensemble Nordlys, The Fidelio Trio, The ConTempo Quartet and Trio Arbós as well as many prominent soloists including Ian Pace, John Feeley, Mary Dullea, Darragh Morgan, Satoko Inoue and David Adams.
McLachlan is also known as a broadcaster and writer on contemporary music, with many published articles.