Option 1
Converging waveforms
Two small waveforms flow down into one wider waveform. Pure audio, clear merge.
Merge audio files — line icons
Simple, single-stroke line icons. Shown large, then at home-page size, then in an accent color and on a dark surface. Stroke scales with size and inherits text color.
Option 2
Funnel
Notes drop into a funnel, a single waveform comes out. "Many into one."
Option 3
Combine inward
Arrows press in from both sides onto one waveform. Compact, very icon-like.
Option 4
Merge branches
Git-merge gesture: two sources join a single waveform trunk. Reads "merge" instantly.
At home-page size
Converging waveforms
Funnel
Combine inward
Merge branches
In an accent color
Converging waveforms
Funnel
Combine inward
Merge branches
On a dark surface
Converging waveforms
Funnel
Combine inward
Merge branches