When you're playing Lux Aeterna, you lose if you run of time. While you can use a smart phone or other device to set a timer at the start of the game, why not use a sound track? Here is Tony Boydell's Spotify list of 10 minutes (or thereabouts) timing pieces you might use while playing.
The Spotify list includes György Ligeti's piece "Lux aeterna" that was used in the film, 2001: A Space Odyssey. Here is a link to a YouTube video of this piece. (9 minutes, 48 seconds)
Alternatively, there are large numbers of timers with music available on the web. Simply, search for "10 minute timer with music" or your own duration to taste. We don't make any specific recommendations here, but you might like to have a look at the following links.
Here's a fun one that you can set to any time of your choosing. It's just visual, but it does have a bomb at the end!