Interesting how similar Shelley's images are to a Shakespeare poem I posted from The Tempest. Beyond the lovely rhythms and words, I read this poem thus: Just as music lingers beyond voices in the mind, as the memory of an odor may stay alive in the nose's sense, and as roses, even when dried and dead, soften the beloved's bed, so the un-named beloved's thoughts will be the stuff of love's dreams.
To --, by Percy Bysshe Shelley-
Music, when soft voices die,
Vibrates in the memory-
Odours, when sweet violets sicken,
Live within the sense they quicken.
Rose leaves, when the rose is dead,
Are heaped for the beloved's bed:
And so thy thoughts, when thou are gone,
Love itself shall slumber on.