He was the fourth child of a clothier John William McAlpin, and his German wife Marie Louise (née Gerdes).
In 1892 Robin Hood, his first dramatic work, was performed at Wellingborough School and that year he was appointed organist and choirmaster at Kensington Presbyterian Church.
In 1897, King Arthur, an opera in three acts, commissioned by impresario Herbert Marshall, was performed by the Leicester Philharmonic Society under H. S. Ellis.
In his thirtieth year McAlpin was appointed organist and choirmaster of Trinity Presbyterian Church Clapham, where his sacred cantata The Prince of Peace had its first performance.
In 1907 McAlpin had his portrait painted by Richard Jack RA, and a bronze bust was sculpted by W. B. Fagan FRBS.