A boy chorister at All Saints Anglican Church in Winnipeg, he then became organist of St Luke's Anglican Church at age fifteen. McLean studied piano in Winnipeg with Russell Standing and organ there, and in Vancouver 1947-8, with Hugh Bancroft. He studied piano in Vancouver with Phyllis Schuldt and in 1949 on an AB scholarship he entered the RCM, where his teachers were Arthur Benjamin (piano), Sir William H. Harris (organ), and W.S. Lloyd Webber (composition). McLean became the first Canadian to receive an organ scholarship to King's College, Cambridge, and while studying there (1951-6) he won the 1954 Arnold Bax Commonwealth Medal and the 1955 Harriet Cohen Bach Medal. He made his London debut in November 1955 at the Royal Festival Hall, performing the Malcolm Arnold Organ Concerto with the Royal Philharmonic Orchestra under Sir Adrian Boult in the annual Royal Command Concert in the presence of Queen Elizabeth II.
McLean returned to Vancouver in 1956 and served 1957-73 as organist-choirmaster at Ryerson United Church. He founded the Vancouver Cantata Singers in 1958 and remained their conductor until 1967; he also led the Hugh McLean Consort 1957-67 in musicologically authentic performances of baroque music for Vancouver audiences and founded the CBC Vancouver Singers. He taught 1967-9 at the University of Victoria and 1969-73 at the University of British Columbia prior to serving 1973-80 as dean of the Faculty of Music at the University of Western Ontario, where he continued to teach organ, harpsichord, and music history in 1991. In 1995, he retired from Western as professor emeritus to become Minister of Music at All Saints Episcopal Church, Winter Park, Florida.
As an organ recitalist, McLean was heard frequently on the CBC and appeared publicly in every major Canadian centre, in San Francisco, Los Angeles and Chicago, and at two of Bach's churches, the Blasiuskirche of Mühlhausen and the Thomaskirche of Leipzig. He also broadcast with BBC, Australian BC, Swiss Radio, and NHK (Japan). In 1975 he performed on Polish radio as a conductor and in 1988 he became the first Canadian organist to tour the USSR. He gave the Canadian premieres of Hindemith's Organ Concerto No. 1 (19 Sep 1970) and No. 2 (16 May 1972) with the CBC Vancouver Chamber Orchestra under John Avison, and was a soloist with the Toronto Symphony, his appearances including performances of Saint-Saëns' Symphony No. 3 (3 and 4 Apr 1979) and of Poulenc's Concerto (12, 13, and 16 Sep 1982) in the inaugural concerts of Roy Thomson Hall on the Gabriel Kney organ that he helped to design. He also performed organ concertos with the Calgary Philharmonic and the NACO. He premiered Bengt Hambraeus' Icons 29 Sep 1975 in Toronto during World Music Week. McLean also toured Great Britain, Japan, Scandinavia, and Switzerland, and gave lecture/recitals and master classes in Germany and Australia. He served as a juror for the 1981 St Alban's International Organ Competition and the 1984 International J.S. Bach Competition in Leipzig.
As a musicologist specializing in 17th- and 18th-century studies, McLean was awarded Canada Council grants in 1960 and 1965 to investigate the Cummings collection of western manuscripts at the Nanki Music Library in Japan, and a further grant in 1972 to travel to Poland and the German Democratic Republic, where he located works by Alessandro Scarlatti (a lost opera) and J.H. Schein. He published editions of the organ works of Purcell (Novello 1968) and J.L. Krebs (Novello 1981) and individual works by Mozart, William Felton (both Oxford University Press 1957), John Blow (Novello 1971), H.N. Gerber (Concordia 1984), and an anonymous 18th-century composer (Oxford University Press 1987). As a consultant for the publications program of the RCMT from 1989 he edited new series of repertoire for voice, violin, and piano that included translations of song texts from French, German, and Norwegian into English, new arrangements of folksongs, and original compositions. He also served on the editorial board of the new C.P.E. Bach edition, wrote 19 articles for The New Grove Dictionary and had others published in the AGO/RCCO Music Magazine, Poland: Illustrated Magazine, DDR-Revue, and the Canada Music Book. He was a contributor to EMC. He presented papers to many learned societies and gave radio talks and reviews. McLean was a director of the Canadian Music Council 1975-80 and was a vice-president 1976-9. He became a fellow of the Royal College of Organists in 1953, a fellow of the Royal Canadian College of Organists in 1957, and in 1985 he became a fellow of the Royal College of Music. In 1977 he was made a fellow of the Royal Society of Canada, in 1987 he was named a Member of the Order of Canada, and in 1990 he received the Order of the Stern der Völkerfreundschaft (German Democratic Republic).
McLean was married to the pianist Anne Stillman (b 1950; DMA British Columbia 1990), a pupil in Edmonton and Calgary of Jean-Pierre Vetter and Boris Roubakine, in Geneva of Eduardo Vercelli, and at the University of British Columbia of Jane Coop. Anne McLean performed and broadcast in Europe, Australia (1987, 1989), and the USA (1991), toured widely in Canada, and recorded contemporary piano works by Canadian composers and others (FLORAN CD-9201). Hugh and Anne McLean performed works for two pianos and piano and organ on the CBC and in Roy Thomson Hall (including the premiere of Derek Healey's Homage F.D.: Rhapsody for Piano and Organ 26 Nov 1986).
'Blow and Purcell in Japan,' MT, vol 104, Oct 1963
Blow, John, Two voluntaries: from the Nanki manuscript, McLean (ed) (Borough Green, Kent, 1971)
''New Polish sources for the German Baroque,' CAUSM J, vol 2, Fall 1972
'Technology in the education of the musician,' ISME Yearbook, vol 2, 1974
'Mozart parodies and Haydn perplexities: new sources in Poland,' Studies in Music from the University of Western Ontario, vol 1, 1976
' Caritas domi incipit: an early 18th-century organ book,' ibid, vol 2, 1977
'The concerted organ fantasia and chorale in 18th-century Germany,' Organist: J of the Japanese Society of Organists, no. 4, 
'Canada: its musical unity and diversity,' Transactions of the Royal Society of Canada, vol 16, 1978
'Krebs's concerted chorales and fantasias,' MT, vol 121, Nov 1981
'Healey Willan and the Tractarian Movement,' Studies in Music from the University of Western Ontario, no. 8, 1983
'Bernard Granville, Handel and the Rembrandts,' MT, vol 126, Oct 1985
'Granville, Handel and "some golden rules",' MT, vol 126, Nov 1985
'The centenary fanfare "RSC/SRC",' Diversa, vol 3, Spring 1987
'Performance practice, form and text in the organ works of Dietrich Buxtehude,' The Proceedings of the International Buxtehude/Scheidt Festival and Conference at the University of Saskatchewan November 1987 (Saskatoon 1989)
'H. Hugh Bancroft,' The American Organist, vol 23, Jun 1989
'The organ works of Heinrich Nikolaus Gerber,' Festschrift for Lady Susi Jeans (Oxford 1991)
'Organ music II' McLean (ed). Ottawa, Canadian Musical Heritage Society. 1997