You can find e-books in Janet online catalog.
e-books:
Dawsonera 
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