When you create a slideshow, it will be automatically saved as a memory.
To change the music or the duration, modify the memory.
But there is no way to create a slideshow without music. You have only the option to find the least annoying or distracting music in the suggested music or in Music, or silence your iPhone, before you play the slideshow.
There is no way to change the speed of a memory either. You can only change the length by adding or removing photos, but the timing is fixed.
See: Make and play slideshows on iPhone - Apple Support
"Slideshows are automatically formatted and set to music.
- Go to the Photos app
on your iPhone. - Swipe down to see the photo grid, then tap Select.
- Tap each photo you want to include in the slideshow, then tap
. - Tap Play as Slideshow.
- Note: Your slideshow is automatically saved as a memory. To view it later, scroll down to the Memories section of the Photos app.
To change the slideshow music, theme, and more, see Personalize your memories.
Change the Memory look
Use Memory looks to apply consistent color and style adjustments to all the photos in a memory.
- Go to the Photos app on your iPhone.
- Scroll down to Memories, then tap a memory to play it.
- Tap the screen, then tap
. - Tap
, tap a Memory look, then tap Done.
Change the music
You can change a memory’s music by choosing from memory soundtracks or suggested songs in Apple Music. Apple Music subscribers can also access their Apple Music library and view suggested songs based on musical preferences or the content of the memory.
- Go to the Photos app on your iPhone.
- Scroll down to Memories, then tap a memory to play it.
- Tap the screen, then tap .
- Tap
, tap a song, then tap Done. - Apple Music subscribers can tap
to search for songs in the Apple Music library."
