Can I limit how many songs a guest can request?

Yes — Max Songs Per Request, in the Settings sub-tab of your Requests tab. Drag the slider anywhere from 1 to 10 songs; the default is 5. It's available on every plan, including the free Starter plan.

The limit is applied in your guests' song picker itself: once someone has selected as many tracks as you allow, it stops accepting additions, so a submission can never arrive over the limit. Setting it to 1 turns the page into a one-song-at-a-time request form, which works well for big crowds where you want breadth rather than a handful of people dominating the queue.

One distinction worth understanding: this caps a single submission rather than a guest's total for the night. Someone can fill the form, send it, and come back later with another batch — the setting stops one person dumping fifteen songs on you in one go, not from participating twice. If you want a firm ceiling on the event as a whole, Pro lets you delete the requests you don't want before you sync.