At Stanford, the couple began a 20-year friendship with Frank Zappa. Rimmer and Harrison together developed an increasing interest in ethnomusicology, with common research trips to Mexico, Central and South America, making recordings of the music-making of indigenous people. During this time, she participated in the establishment of ethnomusicology as an academic discipline at the Institute of Ethnomusicology at the University of California where she published under her married name, Joan Harrison, on Spanish elements in the music of Maya groups in Chiapas, Mexico. This research interest led to Harrison quitting his position at Oxford in 1970 and taking up a professorship in ethnomusicology at the University of Amsterdam in the Netherlands. At all times, Rimmer pursued her own research, now also including music and musical instruments of this country, which resulted in a noted series of publications. In 1976, the couple relocated to Canterbury, where Harrison died in 1987. In addition to her innovative work on musical instruments and in developing the field of ethnomusicology, in her 70s she was breaking new ground in the study of historical dance. At the age of 80 she was still publishing research papers and was on the editorial board of the journal "Dance Research". Joan Rimmer died in Whitstable, Kent, aged 96.