diff --git a/Source/Apps/Tune/hbios.inc b/Source/Apps/Tune/hbios.inc
index f2442f78..2f5d177d 100644
--- a/Source/Apps/Tune/hbios.inc
+++ b/Source/Apps/Tune/hbios.inc
@@ -9,7 +9,8 @@ BF_SYSGET	.EQU	$F8		; HBIOS: SYSGET function
 
 BF_SND		.EQU	$50
 BF_SNDRESET	.EQU	BF_SND + 0	; RESET SOUND SYSTEM
-BF_SNDVOL	.EQU	BF_SND + 1	; REQUEST SOUND VOL - D IS CHANNEL, E CONTAINS VOLUME (255 MAX, 0 SILENT) - SCALED AS REQUIRED BY DRIVER (EG: MAPS TO JUST 4 BIT RESOLUTION FOR SN76489)
-BF_SNDPRD	.EQU	BF_SND + 2	; REQUEST SOUND PERIOD - D IS CHANNEL, HL CONTAINS PERIOD (0 LOWEST NOTE) - SCALED BY DRIVER (EG: MAPS TO JUST 10 BITS FOR SN76489 )
+BF_SNDVOL	.EQU	BF_SND + 1	; REQUEST SOUND VOL - L CONTAINS VOLUME (255 MAX, 0 SILENT) - SCALED AS REQUIRED BY DRIVER (EG: MAPS TO JUST 4 BIT RESOLUTION FOR SN76489)
+BF_SNDPRD	.EQU	BF_SND + 2	; REQUEST SOUND PERIOD - HL CONTAINS DRIVER SPECIFIC VALUE
+BF_SNDNOTE	.EQU	BF_SND + 3	; REQUEST NOTE - L CONTAINS NOTE - EACH VALUE IS QUARTER NOTE
 BF_SNDPLAY	.EQU	BF_SND + 4	; INITIATE THE REQUESTED SOUND COMMAND
-BF_SNDQUERY	.EQU	BF_SND + 5	; D IS CHANNEL, E IS SUBCOMMAND
+BF_SNDQUERY	.EQU	BF_SND + 5	; E IS SUBFUNCTION
diff --git a/Source/Doc/Architecture.md b/Source/Doc/Architecture.md
index 8a7ecfc9..9d61590f 100644
--- a/Source/Doc/Architecture.md
+++ b/Source/Doc/Architecture.md
@@ -1374,7 +1374,7 @@ chip provides.
 | _Entry Parameters_
 |       B: 0x52
 |       C: Audio Device Unit ID
-|       HL: Period (0000=lowest note, FFFF=highest note)
+|       HL: Period
 
 |      _Returned Values_
 |           A: Status (0=OK, else error)
@@ -1383,7 +1383,9 @@ This function sets the sound chip period parameter.  The period will
 be applied when the next SNDPLAY function is invoked.
 
 The period value is a driver specific value.  To play standardized
-notes, use the SNDNOTE function.
+notes, use the SNDNOTE function.  A higher value will generate a lower
+note.  The maximum value that can be used is driver specific. If value
+supplied is beyond driver capabilities, register A will be set to $FF.
 
 ### Function 0x53 -- Sound Note (SNDNOTE)