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13. Turning audio files into Serum wavetables
1 Xfer Records Serum lets you easily resynthesise any audio file into a wavetable oscillator. Although you can try converting absolutely any audio, it's recommended to use a low-tuned singlenote sample with a consistent pitch. To demonstrate, we've provided a collection of one-shot synth samples in this issue's Tutorial Files folder.
2 If you don't know your sample's pitch already, drag it over Osc A's wavetable display and drop it onto one of the import options that appears. Import: Normal (Dynamic Pitch Follow) should generally be the first option you try. However, if you know the pitch of your sample, there's a better way to import it…
3 As we know 808 Dist F.wav's pitch, click Osc A's pencil icon to open the Wavetable Editor window. In the horizontal Formula Parser strip, click and type F0. Now drag 808 Dist F.wav onto the editor, and Serum will analyse the sample in 1010-sample-long chunks and resynthesise it into a wavetable oscillator.
4 Different DAWs confusingly use different octave standards, so use a spectrum analyser if you need to measure your sample's fundamental frequency before importing. 808 Dist F.wav's fundamental frequency is 44Hz, meaning it's an F1 note. But as in the previous step, telling Serum our sample was F0 gave a better result. Experimentation is key!
5 Our sample has been divided into 87 individual frames, indicated by the bottom horizontal row of numbered Thumbnail overviews. Click through the thumbnails: you'll notice that each frame contains approximately one wave cycle. Play a MIDI note as you click through the thumbnails, in order to audition one of these static frames.
6 Next, it's a good idea to refine the scanning through the frames. As we converted a punchy 808 bass sample, our wavetable has a clicky ‘thump' at the start. To smoothen the back and forth motion through the 'table, we can trim away unnecessary frames from the start and end of the wavetable…
7 To delete the frames containing this ‘bump', select Thumbnail 10 and click the Add/Remove menu and choose Remove: Beginning to Selected. Next, to delete the final few inconsistent frames, select frame 68 and choose Add/Remove » Selected to End. Now scan through the wavetable's multiple frames: the interpolation is smooth and consistent.
8 Our wavetable oscillator contains only 67 frames of a maximum 256. Select one of the Morph options (we choose Morph » Crossfade), and Serum fills in the remaining gaps with interpolated wavetables for even smoother motion between them all. From here, you can manipulate and process your wavetable like any other synth oscillator.