# Rotating stereo

I came up with this fancy effect. I have a stereo recording with instruments panned all over the field from left to right. Then I run this effect on the sound, which makes all instruments travel around, kind of rotating or oscillating from left to right. It starts with all instruments going to the left. The left most instrument turns around first and starts moving to the right, while meeting the others. Soon all move rightwards. Etc.
I’ve tested this only on a stand alone program, which reads a wav file and plays the effect, but it sounded promising, so I thought of implementing it as a plugin in Audacity. Anyone know if this is already done? One could mark a section of a stereo track and run this effect and the whole section could be stereo rotated n times. Rotating only halfway would leave the sound in a phase error and left and right channels switched.

How are you panning each individual instrument if they all reside in one stereo clip?

I’d like to hear this effect, can you post an example?

There are a few panning effects here, but all of them work on individual tracks and I don’t think any of them oscillate.

I’m sure one of the developers would like to hear about this, if you want it included in a future version of Audacity, email or private message galeandrews.

The idea is actually so simple, that I’m sure it must have been done before. Imagin that the left channel is drawn in a XY-coordinate system and the right channel in XZ-system, X being the time and Y and Z the left and right channel elongation respectively. The two channels are drawn as a curve in a 3D space. When you twist this curve around X-axis by 90°, the left channel has become the right channel and the right channel has become the left cannel inverted. Twist another 90° and you’re back in start stage but both channels inverted. At each stage of the rotation, the projection of the 3D curve on XY-plane is what the left channel plays and the projection on the XZ-plane is what the right channel plays.

Check the two mp3 files below. The first one is the original recording. You hear a banjo (actually an ukulele) to the far left, a fiddle to the far right and a blues harp in the middle together with a bass and drums. In the second sample the instruments start rotating. Unfortunately my Mac couldn’t actually save the rotating sample digitally, only play it, so I recorded it with Audacity while I played it with my application, so the samples are not of identical length. While you’re listening on the rotating sample, focus on two instruments at a time.

Chickens

Twisted Chickens

Use headphones when listening to the samples. The instruments in the middle start to go to the left. When they come back and cross the middle point, they are technically in a phase error (one channel inverted), which might sound like the direction were not very clear.

Cool effect. It took a little bit of visualizing, but I get what you’re saying. I’m sure people would get some good use out of it as long as you can choose the rotate speed.

The rotating speed would be determined by the length of the marked section that be rotated, along with the number of rotations inside the section. It could also be interesting to have this implemented on a mixer board. An endlessly rotating knob.

Actually, thinking loud, I might develop my application into a demo program, where you can read a wav, place a start mark and a stop mark inside the sound track, and choose some rotating options like number of rotations, direction of rotation, or some graphic window, where you can draw a freehand curve that defines the rotated angle at every point along the time axis. Most of all I would like to have a developer’s tool kit for making Audacity plugins using a C++ compiler.

The Nyquist Ramp panning plug-in will simply pan a track from one side to the other (so that at the start and end it’s all only in one of the speakers) and the same can be done in Audacity by duplicating the track, panning one hard over in one direction and the other on the opposite direction, then fading one out and the other in. But you don’t need access to the instruments as individual tracks for what you are doing, do you?

I have seen what I assume to be similar ideas in spatialiser plug-ins but they go farther in that they try to rotate both axes in circular fashion so that you sense the sound moving behind and in front, and above and underneath.

If you wanted to discuss your ideas with the developers really you need to subscribe to the audacity-devel mailing list:
http://lists.sourceforge.net/lists/listinfo/audacity-devel

and post a message.

Thanks for writing.

Gale Andrews

No. The samples in my link show it. The latter sample is completely done out of the former sample, which is just a 2 channel stereo recording. Although done originally as a multi track midi sequence.

That sounds strange. How can it rotate or oscillate vertically, when the idea of stereo is horizontal, as well as our ears? Of course you might have a 4 channel stereo, kind of one channel in each corner of your screen. But even that requires the listener to tilt his head to recognise the vertical dimension of directions.