The roughly out-of-the-box setup as a regular user works fine (meaning the site appears at http://myserver.com:4040). From ps aux

java -Xmx100m -Dsubsonic.home=/var/subsonic -Dsubsonic.host=0.0.0.0 -Dsubsonic.port=4040 -Dsubsonic.httpsPort=0 -Dsubsonic.contextPath=/ -Dsubsonic.defaultMusicFolder=/var/music -Dsubsonic.defaultPodcastFolder=/var/music/Podcast -Dsubsonic.defaultPlaylistFolder=/var/playlists -Djava.awt.headless=true -verbose:gc -jar subsonic-booter-jar-with-dependencies.jar

but just giving an https port

java -Xmx100m -Dsubsonic.home=/var/subsonic -Dsubsonic.host=0.0.0.0 -Dsubsonic.port=4040 -Dsubsonic.httpsPort=6060 -Dsubsonic.contextPath=/ -Dsubsonic.defaultMusicFolder=/var/music -Dsubsonic.defaultPodcastFolder=/var/music/Podcast -Dsubsonic.defaultPlaylistFolder=/var/playlists -Djava.awt.headless=true -verbose:gc -jar subsonic-booter-jar-with-dependencies.jar

makes http://myserver.com:4040 say

HTTP ERROR: 404
NOT_FOUND
RequestURI=/index.view
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and https://myserver.com:6060 say

Unable to connect

I'm only making the change by doing

# SUBSONIC_ARGS="--port=80 --https-port=443 --max-memory=120"
SUBSONIC_ARGS="--max-memory=100 --https-port=6060"

in /etc/default/subsonic and issuing a sudo service subsonic restart (this is Ubuntu Oneiric)