Roll the guitar volume dial down to zero. This mutes the output.
Hit "Record." Once rolling, play a note on the guitar and gradually turn the volume dial up to full. Because the guitar was muted for the attack, only the decay and ambience of the note are recorded.
Roll the volume dial back to zero and repeat the technique. This process is most suitable for slow guitar melodies. It's impractical to play a complex or fast melody while operating the volume dial.
Plug an instrument cable into the input jack of a noise-gate unit and connect the other end to your guitar. Plug a second instrument cable into the output of the noise gate and into your guitar amplifier.
Turn the "Threshold" dial to the maximum. A noise gate mutes all signal below a certain level. Only when the volume threshold is breached does the device unmute the signal. By setting the threshold to the maximum, the gate will allow the signal to pass to the amplifier only when the note reaches full volume. The note can reach full volume only when it is ringing out. The gate therefore mutes the attack, leaving only the decay and ambience.
Turn the pedal on before recording. Test the guitar to make sure the attack is muted.
Double-click the guitar track to open the sample editor window. The sample editor lets you view the audio as a wave-form graphic. It represents notes as peaks and silences as flat lines. The higher the peak, the louder the note.
Click "Tools" and select "Automation." This opens an automation window inside the sample editor. Automation lets you "draw" the level of the volume underneath the sound waves. A line sloping upward from left to right creates a fade-in.
Click "View" and select "Zoom." Click the "+" symbol until one sound-wave peak fills most of the window. Click and hold your cursor below the bottom line in the automation window, level with the left side of the sound-wave peak. This sets the volume at the start of the peak to zero. Drag the cursor right and up. As you do, a sloping line will appear in the automation window. Release the cursor when the line reaches the right side of the sound-wave peak.