Command 0x09: Pitch bend (negative direction)

Sets a pitch bend. Uses the change amount with its sign inverted.

Syntax

0x09, byte delay, byte interval, byte count, sbyte delta, byte reverse

Parameters

Parameter	Type	Description
delay	byte	Time until the first change (interval if 0)
interval	byte	Interval between changes
count	byte	Total number of changes
delta	sbyte	Pitch change per step. Set with its sign inverted
reverse	byte	Number of initial changes applied with the sign inverted

Description

On every key-on, enables a pitch bend that changes the pitch by a fixed amount at fixed intervals (effect enable flag bit0). The setting applies to all subsequent notes until cancelled with command 0x0A.

The pitch bend works as follows.

Initialize each counter at key-on.
If delay is not 0, make the first change when the delay time has elapsed. If delay is 0, make the first change when the interval time has elapsed.
After that, change the pitch every interval. For the first reverse changes, apply the change amount with its sign inverted; after that, apply the change amount as is.
End the pitch bend once it has changed count times (including the reverse changes).

The change amount is added directly to the DSP pitch register value (14 bits, $1000 = original pitch), not to the note number. Therefore, the same change amount produces a smaller change in musical pitch the higher the note.
Effect times are counted in timer periods independent of tempo (about 7.5ms by default; changeable with command 0x2A). For details, see Sequence data structure.

This command takes no time to process; the following event is read within the same tick.

The only difference from command 0x08 is that delta is set with its sign inverted.

Note

If count is 0, it changes 256 times.
It changes the same pitch value as vibrato, so if both are enabled their effects add up.
On a BGM channel under SE interrupt, no key-on is performed, so the counters are not initialized.