Aux Pulse Channels - Risa Tracker

Risa has two auxiliary pulse channels, one attached to each native pulse track:

PU1 can also drive MMC5 pulse 1.
PU2 can also drive MMC5 pulse 2.

The aux pulses are not full extra sequencer tracks. They share the parent pulse track's phrase position, chain/song timing, instrument, duty, volume context, and mute state. Use them for lightweight doubles, intervals, echoes, and simple independent second notes on the pulse tracks.

Aux pulses require MMC5 expansion audio support. Without it, the native pulse tracks still play but the aux pulses are silent. On NES hardware, expansion audio also requires a small console modification; expansion-audio mod guides are available online.

Phrase AUX Column

On PU1 and PU2 phrase screens, Risa can show a second note column:

NTE AUX IN FX

The AUX column appears when the phrase already contains aux notes, or when the selected pulse instrument has AUX set to FREE. This column is only for the FREE mode described below.

AUX notes work like lightweight note events:

A note triggers the matching MMC5 pulse.
A note-off stops the matching MMC5 pulse.
An empty cell does nothing.
An aux-only row can trigger without a parent NTE note.
Copy, cut, and paste treat the aux note as its own phrase cell.

The aux note uses the parent pulse instrument's duty and current effective volume. It does not have its own instrument or FX cells.

Instrument Settings

Pulse instruments have three aux-related settings:

AUX    OFF / DET / INT / ECHO / FREE
PITCH  or DELAY, depending on AUX mode
ATT    0..F

ATT is aux attenuation. 0 uses the same effective volume as the parent pulse. 1..F subtracts that amount from the parent pulse's current volume, after envelope and table volume have been applied, clamped at zero.

The PITCH field is contextual:

In OFF, DET, and FREE, it is the parent pulse fine pitch value.
In INT, it is the aux interval in signed semitones.
In ECHO, the UI labels it DELAY, and it is the echo delay in sequencer ticks.

Signed byte values use the usual tracker encoding: 01..7F are positive, 80..FF are negative two's-complement values.

AUX Modes

OFF disables the aux pulse for the instrument. A parent note in OFF mode will stop an active aux pulse on that track.

DET automatically plays an aux note whenever the parent pulse note triggers. It uses the same musical note as the parent, but applies fine pitch in the opposite direction. This is intended for small detuned doubles. The phrase AUX note column is ignored in this mode.

INT automatically plays an aux note whenever the parent pulse note triggers. The aux note is the parent note plus the instrument PITCH interval. Examples: 07 gives a fifth above, 0C gives an octave above, and F9 gives a fifth below. The interval is clamped to the valid pulse note range. In this mode the instrument PITCH value is not parent fine tuning; live Fxx fine pitch still tunes the parent track, and the aux interval follows that live fine tuning.

ECHO automatically plays a delayed copy of the parent pulse note. DELAY=00 fires immediately; 01..FF waits that many sequencer ticks.

When the parent note triggers, Risa snapshots:

the parent note
the effective aux volume
the instrument envelope

The echo does not follow later parent notes, pitch FX, table transpose, or table FX. Duty is the exception: the echo uses the parent pulse duty that is live when the delayed echo fires. Each fired echo also gets a tiny alternating +1/-1 fine-pitch dither to reduce exact unison phasing against the parent pulse.

Delayed echoes use a two-slot queue:

queued echoes fire oldest first
only one echo can sound on the matching MMC5 aux pulse at a time
if both slots are full, new parent notes are ignored
DELAY=00 echoes fire immediately and do not use the queue

Stops are handled separately:

a later parent note does not silence the active echo
parent OFF is also delayed; it queues a delayed silence
if the queue is full, parent OFF replaces the last slot so the silence stays last
with DELAY=00 and an empty queue, OFF silences the active echo immediately
Kxx is a hard stop: it clears pending echoes and the active echo immediately

Same-row Exy envelope changes are not applied to the echo copy.

FREE uses the phrase AUX note column as an independent second note lane. The aux note is still tied to the parent pulse track's timing and instrument, but it can have a different note event from the parent row. FREE aux notes honor the instrument transpose setting: when TRANS is on, chain and global transpose apply to aux notes. The current track fine pitch applies as well. The AUX column is stored with the phrase itself: reusing the same phrase number on PU1 and PU2 reuses the same aux notes, routed to that track's attached MMC5 aux pulse.

What AUX Follows

Active aux pulses share parent pulse state for tone color and volume. This is most direct for DET, INT, and FREE; ECHO uses the snapshot and live-duty rules described above.

Instrument duty and volume.
Wxx duty changes from phrases or tables.
Exy envelope volume changes.
Table volume scaling.
Rxy volume changes.
Parent track mute/unmute.
Parent note-off and Kxx kill. In ECHO, parent OFF follows the echo delay, while Kxx clears immediately when the kill fires.

Aux pulses do not bind or advance tables on their own. The parent pulse track has the only table runtime; table rows can still affect active aux output through the shared duty and volume context listed above. For ECHO, later table pitch changes do not retune a pending or active echo.

INT and ECHO also honor delayed parent notes: if a parent note is delayed with Dxx, the automatic aux trigger is delayed with it. In FREE, an aux note in the AUX column fires at the row boundary even if the parent NTE note is delayed.

What AUX Does Not Implement

Aux pulses do not have independent instruments, tables, FX columns, envelopes, sweep, or per-row volume/duty settings. The only per-row aux data is the AUX note cell in FREE mode.

FREE aux notes honor the instrument TRANS setting for chain and global transpose, but they do not apply the parent table's current transpose.

Aux pulses do not mirror parent pitch FX after triggering. The parent pulse can keep using Cxy, Pxx, Vxy, Lxx, Qxy, and Sxy, but those pitch changes are not applied continuously to the MMC5 aux pulse. Aux pitch is a row-triggered snapshot plus the static behavior of the selected aux mode.

Use INT for fixed harmony, DET for fine detune, ECHO for delayed copies, and FREE for explicit second-note events. Use the native pulse track when a line needs full pitch FX or independent sequencing.