https://www.discogs.com
https://www.45cat.com
https://www.45worlds.com
https://www.allmusic.com
https://secondhandsongs.com
https://adp.library.ucsb.edu (DAHR)
https://www.20sjazz.com/ (Twenties Jazz)
https://www.jazzdisco.org/ (Jazz Discography Project)
https://www.siue.edu/lovejoy-library/musiclistening/NRJA/ (National Ragtime and Jazz Archive)
https://www.ibiblio.org/folkindex/index.htm (Folk Music Index)
https://www.ibiblio.org/hillwilliam/BGdiscography/ (Bluegrass Discography)
https://www.wirz.de/music/america.htm (Stefan Wirz' American Music)
http://musiktiteldb.de/index.html (Ultimate Music Database [in German])
https://archive.org/details/audio (Internet Archive: Digital Library)
http://rcs-discography.com/rcs/index.html
http://countrydiscography.b l o g s p o t.com (Praguefrank's Country Music Discographies)... VL won't allow a clickable link to this URL
http://www.78discography.com
https://www.1959bhsmustangs.com/VideoJukebox.htm (Paul's Video Jukebox)
https://www.ultratop.be/nl
https://bandcamp.com
https://rateyourmusic.com/
https://www.ascap.com/repertory (US ASCAP)
https://repertoire.bmi.com/StartPage.aspx (US BMI)
https://www.apraamcos.com.au/works-search (Australia)
https://www.socan.com/jsp/en/mem/pubRepertoireSearch.jsp (Canada)
https://www.sesac.com/#!/repertory/search (Europe)
https://repertoire.sacem.fr/en (France)
https://online.gema.de/werke/search.faces?lang=en (Germany)
https://www2.jasrac.or.jp/eJwid/main?trxID=F00100 (Japan)
PRS (UK): No link. PRS doesn't have a public search option.
https://en.wikipedia.org
https://www.youtube.com
https://music.metason.net/ (searchable artist info)
https://www.lyrics.com (one of the best lyrics sites for composer info)
https://www.azlyrics.com (another best lyric site for songwriter info)
https://bandchirps.com/ (bios on big band vocalists and band leaders)
https://www.uncamarvy.com (Marv Goldberg R&B Notebooks)
https://garagehangover.com/ (60s garage bands)
http://doo-wop.blogg.org/ (Doo Wop Groups: Biography & Discography)
https://southerngaragebands.com/ (Southern Garage Bands)
https://www.popgoesthe60s.com/ (excellent band biographies on YouTube)
https://rstrathdee.com/artistsIndex.htm ("The Best Years of Music")
http://heybabydays.com/ (Heeey Baby Days of Beach Music)
http://campber.people.clemson.edu/rsrf.html (various artists)
https://www.adducation.info/general-knowledge-rock-pop/ (lists & quizzes)
https://musicmap.info/
https://artfarmer.org
http://jimsrootsandblues.com/music-of-bill-monroe/
https://www.bingmagazine.co.uk/bingmagazine/crosby.html
https://www.dorisday.net/forum/viewtopic.php?t=3061
http://ellingtonweb.ca/
http://www.deaddisc.com/ (Grateful Dead Family Discography)
https://www.iannis-xenakis.org/
https://www.uncamarvy.com/OriginalInkSpots/Original-Ink-Spots.html
http://www.joemeekpage.info/
https://www.margaretwhiting.com/discography.htm
http://www.walterdonaldson.net
more to be added as I find them
https://gils-playlist.weebly.com/past-shows.html