You can find e-books in Janet online catalog.
e-books:
Dawsonera 
Dawsonera is no longer available as of July 2020.
Ebrary
Ellibs
eBook Collection (Ebsco)
e-magazines and journals:
IIMPFT (International Index to Music Periodicals) - music periodicals and journals
RILM (Abstracts of Music Literature) (on trial 2016)
Academic Search Elite - humanistic, sociological
DOAJ Directory of Open Access Journals - multidisciplinary
Elsevier Science Direct - multidisciplinary
ABI/INFORM - business, marketing, arts
PubMed - music therapy, medicine
ERIC - music education, pedagogy - domestic articles
Aleksi - domestic periodicals
ARTO - domestic articles
e-recordings and videos:
Naxos Music Library
Naxos Music Library Jazz
Raita - music from old records
e-sheet music:
ISMLP (Petrucci Library)
e-Concerthouse
Verkkovirsikirja
Neue Mozart-Ausgabe Online
Digitaalisia nuotteja - Sibelius Academy list
Suomen kansan eSävelmät - Digital archive of Finnish Folk Tunes
e-dictionaries and indexes:
Grove Music Online
Music Finland
AllMusic
Library databases:
Janet - JAMK library
JykDok - Jyväskylä University library
Keski-Kirjastot - Jyväskylä city library
ARSCA - Sibelius Academy library
MELINDA - union catalogue of Finnish libraries
VIOLA - union catalogue of Finnish music libraries
Janet Classic - old library database
Learning materials:
MuHi - music history
MuTe - music theory
Musiikinteoria 1 - Sibelius Academy, music theory
Musiikinteoria 2 - Sibelius Academy, music theory
1900-luvun musiikin historia - Sibelius Academy, music history
Opi verkossa - Sibelius Academy, e-material for music learning
Suomalaisen musiikin historia - Warner
LAURA - lyrics, translations
Other tools:
Finto - finnish thesauri
Suomen Musiikkikirjastoyhdistys ry publications
Music Finland
RefWorks - research management, writing and collaboration tool
musicinfo
Music Timeline
Music archives:
Suomen äänitearkisto
Suomen Kansan eSävelmät - Digital archive of finnish folk tunes
LYYRA - Finnish music archives (pdf)
Sibelius-Akatemian arkisto
JAPA - Finnish Jazz & Pop archive
Pomus - A Museum of Finnish Popular Music
Every Noise at Once
Arkistoja - Sibelius Academy list
Radio- ja TV-arkisto - can only be used at JU digiroom B228
Bach Bibliograpfy
Beethoven Gateway
DRAM