When Rhythmbox plays no other software is able to use sound

[Foss User <fossist@gmail.com>]

When i run rhythmbox, any other software is unable to produce sound.
similarly, when some software is already producing sound rhythmbox is
unable to play songs.

but if i don't use rhythmbox, other multiple audio software can run
and produce sound at the same time. what's wrong with rhythmbox?

I used lsof commands to see what files are opened by the various music players.

rhythmbox is opening some file /dev/shm/pulse-shm-foo while vlc and
other audio software is opening /dev/snd/pcmFOO

FOO or foo are placeholders i am using instead of some numbers.

please help.