Reels templates need music and 3 clips: build the match in Timeline

Short answer

Instagram's Reels feature page says a template needs music and at least 3 clips, that you can record clips adding up to 20 minutes, and that Reels over 3 minutes will not be recommended to new audiences. If you want to reproduce the pattern outside the app, a 3-slot Sume Timeline with a soundtrack is the equivalent: three video slots, one music bed, a short total length.

The template idea is rhythm: cuts land on the beat. Timeline cannot detect beats for you, but it lets you set each slot's duration, with a minimum of 0.2 seconds, so you can place cuts on times you choose.

Mapping the pieces

Instagram's rules on the left, the matching Sume setting on the right.

Building the three-slot cut

Pick a music track first and note where its beats fall. Then set slot durations that sum to the track length you want. A 15-second Reel with three slots is 5 seconds each; a faster edit uses six slots of 2.5 seconds. The unbilled plan call returns duration_seconds and segment_count so you can check that the totals match before you spend anything.

Add a short transition between slots if you want one. Timeline supports fade, wipeleft, wiperight, slideup, slidedown and dissolve, up to 1 second each, with up to 8 chained. For beat-synced content, hard cuts usually look cleaner than long transitions, so leave transitions off unless the style needs them.

• Use soundtrack.loop only if the music is shorter than the video.
• Set soundtrack.fade_out_seconds (up to 10) so the music ends with the picture.
• Output defaults to 1080x1920 MP4, which suits Reels.
• Inputs must already be media.sume.com URLs from your workspace; Timeline does not fetch other hosts.

Template or exported file

An in-app template will use the app's own music library and sync features, so it is the right tool when you are posting from a phone. A Timeline render is the right tool when the clips are generated or when you need to repeat the same structure across many products. Both end as a vertical video; what differs is who sets the cut points.

The 3-minute line is worth keeping in mind for either route. Instagram's page says longer Reels will not be recommended to new audiences, so a Reel meant to reach people who do not follow you belongs under 3 minutes. See the 20-minute versus 3-minute post for that distinction.

Quick checklist

Before you render, confirm that the music has a clear end, that each slot is at least 0.2 seconds, that total duration is what you intended, and that no slot is so short the viewer cannot read the frame. Three clips in a 9-second Reel means 3 seconds each, which is enough for a single idea per clip.

• Pick the track and decide the length first.
• Set slot durations that sum to the length.
• Run the plan call and read duration_seconds.
• Render, then view on a phone before posting.