Arpeggios disable the "length" bit in NRx4

[ISSOtm]

fortISSimO/fortISSimO.asm

Lines 1119 to 1122 in b51ebdb

	ld a, 0
	adc a, [hl]
	; TODO: whoops, where did the ctrl mask go? But there's not enough room...
	ldh [c], a

As the comment mentions, this is blocked by #2, since there isn't enough room to fit extra instructions in this code.

[ISSOtm]

Turns out the fix is fairly simple:

diff --git a/fortISSimO.asm b/fortISSimO.asm
index 298da85..71145e1 100644
--- a/fortISSimO.asm
+++ b/fortISSimO.asm
@@ -1101,12 +1101,14 @@ FxArpeggio:
 	ld hl, whUGEch1.period - whUGEch1.note
 	add hl, de
 	add a, [hl]
-	ldh [c], a
 	inc hl
+	ldh [c], a
 	inc c
-	ld a, 0
-	adc a, [hl]
-	; TODO: whoops, where did the ctrl mask go? But there's not enough room...
+	ld a, [hld]
+	adc a, 0
+	dec hl
+	assert whUGEch1.period - 1 == whUGEch1.ctrlMask
+	or [hl]
 	ldh [c], a
 	ret
 

...but hUGEDriver also overwrites the flag.

https://github.com/SuperDisk/hUGEDriver/blob/5e4c77d2abbfeb75e80b4d0da1ddc370053e1c88/hUGEDriver.asm#L1081

https://github.com/SuperDisk/hUGEDriver/blob/5e4c77d2abbfeb75e80b4d0da1ddc370053e1c88/hUGEDriver.asm#L424-L427