Why Does Mono Audio Draw a Diagonal Line in OSC-1?
In OSC-1's XY view, the left audio channel sets horizontal position and the right channel sets vertical position. If both channels carry the same signal at the same level, every point has matching X and Y values, so it falls on a diagonal. A mono signal duplicated to both channels has this relationship.
Hi, I'm Trina with BeamTracer.com. When a track gives me a line instead of the drawing I expected, I check the two channels first. This native recording keeps the same generated tone and changes Phase Y from 0° to 90°, then 180°.
Press play for the native stereo sound and XY picture. The recording begins with matching channels, changes to a circle, then ends on the opposite diagonal. Start with your volume low. Playback that mixes stereo to mono will change what you hear.
Before you start
These demonstrations were recorded in desktop Chrome with Studio access. The first video includes the generated stereo sound; the settings walkthroughs are silent. Your plan controls export resolution, watermark and allowance. See plans and export limits.
How can I reproduce the diagonal?
Open OSC-1, choose CREATOR, expand GENERATORS and open LISSAJOUS. Select Circle from PRESET, then use these values:
| Control | Value |
|---|---|
| Freq X, Freq Y | 1, 1 |
| Amp X, Amp Y | 0.50, 0.50 |
| Phase X, Phase Y | 0°, 0° |
| Speed | 0.50x |
| T Range | 100% |
Keep the display in XY for this comparison. The captures use MODERN DIGITAL. If you have enabled SWEEP, switch it off so the main comparison remains the XY trace.
Both generated signals now reach each value together. The moving point travels back and forth along the same diagonal; persistence lets you see the whole line. This models identical audio in both stereo channels. It does not identify the original file's channel count: a stereo file can contain identical channels too.
Why does changing phase make a circle?
Leave both frequencies and amplitudes fixed. Change Phase Y to 90°, keeping Phase X at 0°. The vertical signal now reaches its peaks a quarter-cycle apart from the horizontal signal. With these equal-amplitude sine waves, the XY trace becomes a circle, as illustrated in Tektronix’s Lissajous phase chart.
The left-side Phase Y setting changes while the generator keeps playing. This UI walkthrough is silent; use the first clip for the source sound.
At 180°, one channel is the inverse of the other. Their values have opposite signs, so the trace becomes the opposite diagonal. This particular example uses a steady sine wave; an arbitrary stereo recording can make a much more complicated picture.
Circle to opposite diagonal: only Phase Y changes from 90° to 180°.
What if the trace is an ellipse?
Unequal channel levels can flatten a circle. With the same 90° phase difference, lower Amp Y from 0.50 to 0.20. Horizontal travel stays the same while vertical travel shrinks.
Amp X stays at 0.50. Amp Y drops to 0.20, making the trace shorter vertically.
Phase changes can also create ellipses, so the shape alone cannot tell you whether the levels match. Use a known source and change one control at a time before diagnosing a track or interface.
Why is the line horizontal or vertical instead?
A horizontal line means vertical movement has disappeared; a vertical line means horizontal movement has disappeared. You can approach a horizontal line with the Lissajous generator by lowering Amp Y to its minimum, 0.10, while Amp X stays at 0.50. That leaves a thin ellipse because this control stops above zero.
Amp Y drops to 0.10. Some vertical movement remains. A completely absent right signal would leave a horizontal line.
For an imported track or live source, check its stereo routing and balance. A mono source may be duplicated to both channels or routed to only one, depending on the source and routing. If both channels are silent, expect no traveling trace; persistence may leave an old picture visible briefly.
Can a display setting restore a stereo drawing?
Changing glow, color or persistence cannot recover channel differences that were removed by a mono mix. Use the original stereo source when the drawing depends on separate left and right signals. For a known test, restore Amp X and Amp Y to 0.50, Phase X to 0° and Phase Y to 90°; this generator should return to a circle.
If your question is about a waveform moving sideways over time, use the Sweep trigger lesson. Sweep plots a signal against time, so its diagnosis differs from a diagonal in XY. For a deliberate shape, continue with the Lissajous generator guide.