diff --git a/papers/doc/7-systems/x1_010.md b/papers/doc/7-systems/x1_010.md
index e2e44f18..76517b64 100644
--- a/papers/doc/7-systems/x1_010.md
+++ b/papers/doc/7-systems/x1_010.md
@@ -21,6 +21,7 @@ Another one ("Envelope") is 4 bit stereo waveform, its multiplied with above and
 These are stored at upper half of RAM at common case.
 
 Both waveforms are 128 byte fixed size, its freely allocated at each half of RAM except channel register area: each half can be stored total 32/31 waveforms at once.
+in furnace, You can set envelope shape split mode. when it sets, its waveform will be splitted to left half and right half for each outputs. each max sizes are 128 bytes, total 256 bytes.
 
 # effects