Creating natural-sounding loops requires experimentation. Many factors can cause pops and glitches, but the following guidelines will help you to create loops with less trial and error.
Match endpoint amplitudes
It’s most common for the endpoints of a loop to occur at zero-crossings.
Match endpoint waveform slopes
If the slope of a waveform changes drastically, an audible pop will be produced.
Match endpoint sound levels
The overall loudness within ~100 ms of the endpoints should be equal.
Avoid very short loops
If the loop is shorter than ~50 ms (1/20 Hz), you will most likely create a loop with a pitch not equal to the sample pitch.
You can experiment with pitch-tuning by creating short loops with a length of 1/frequency. For example, if your had a sample pitch of 440 Hz (A5 on the MIDI keyboard), you can make the loop 2.27 ms. Pitched loops, however, do not sound like the original sample.
Click the Play Pre-Loop button to play the sound data before the selected loop.
Click the Play Loop button to play the selected loop. You can use the Loop Tuner to tune the loop during playback.
Click the Play Post-Loop button to play the sound data after the selected loop.
When your Sample Type is Sustaining with Release, you can click the Loop Select button to switch between the sustaining and release loops in the Loop Tuner.
When the sustaining loop is selected, the button is displayed as .
The Loop End Position and Loop Start Position boxes display the current positions (in samples) of the endpoints. Use the spin controls to adjust the end points.
Each loop end window includes buttons to move the loop endpoint to the next or previous zero-crossing:
Click the Zero Crossing Left button to move the endpoint to the previous zero-crossing.
Click the Zero Crossing Right button to move the endpoint to the next zero-crossing.
To configure the zero-crossing finders, choose Preferences from the Options menu and click the Editing tab. You can modify the Snap to zero-crossing slope, Zero-cross scan time, and Zero-cross level threshold settings to determine how Sound Forge software locates zero crossings.
Click the Lock Loop Length button if you want to shift a loop’s position without changing its length. When this button is selected, any operation you use to change a loop point affects both the start and end of the loop, therefore keeping the loop length constant.
This button also controls the Lock Loop/Region Length command on the Options menu.
If you want to save loop points in your file, select the Save metadata with file check box in the Save As dialog.
From the View menu, choose Loop Tuner to open or close the Loop Tuner window. You can use the Loop Tuner to adjust the starting and ending points of a loop (or selection) to create smooth transitions.
The Loop Tuner allows you to view both loop endpoints at once. The left-hand side of the Loop Tuner window shows the end of the loop, while the right-hand side shows the start of the loop. A seamless loop will not have any discontinuities; the waveform should look smooth as it goes from the end of the loop back to the start.
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