New Note Actions (NNA)

What it is#

impulse-tracker's answer to channel scarcity: when a new note starts in a channel, the instrument's NNA says what happens to the note still playing — cut, continue, note off (release) or note fade — and the old note keeps sounding in a virtual channel. A piano run with sustain no longer needs four or five channels: "by simply giving the default NNA of 'fade' to a piano sample a nice keyoff sustain can be accomplished" (source: s-tw081-it-tip-of-the-week).

How to do it#

Impulse Tracker#

• Set the default NNA in the instrument (with a sensible fade-out so virtual channels are freed).
• Override per note with S73 cut · S74 continue · S75 note off · S76 note fade — the setting applies to the note following the command. Correction from IT's author: a note left with S74 keeps ringing until an S70 past-note cut; ^^^ only affects the latest note; check the info page's Tot column to see how many virtual channels you are burning (source: s-tw081-it-tip-of-the-week).
• Instruments cost almost nothing in file size, so keep several per sample with different NNAs and fades.
• MIDI instruments: IT sends NOTE OFF when the note's tracker volume reaches zero, so NNA note fade with a fade-out (Airon's was 120) delays every note-off; use note cut and fade-out 0 for tight timing, or keep note fade with a small fade-out as a deliberate legato — "the greater the VOLUME FADE, the less LEGATO"; ^^^ sends NOTE OFF at once (midi-in-trackers; source: s-tw098-impulse-tracker-midi).
• Continue is for drums and short unlooped samples; a looped sample with continue and no cut "will annoy the listener into deleting your song" and can crash the player. Zinc: use NNAs, but "don't cram your instruments into one or two channels" (source: s-tw075-it-percussion-tips).
• The 1996 objection: kal-zakath relayed the view that NNAs "encourage inefficient tracking, and reduce GUS sound quality"; vegas did not use them but called them "definitely not useless", citing FutureAssassin's NAID '96 entry as the good example (source: s-tw062-interview-vegas). The manual supports the second half of the complaint mechanically — on a gravis-ultrasound the playback rate falls as active channels rise (source: s-it-manual) — and Pulse's own hope (below) that NNAs would not kill four-channel craft answers the first.

The Modsquad's drum-sampling comparison (1997): a kick-plus-snare combination sample versus playing the two with NNA continue — "almost the same" result, minus the interaction of the two waveforms, the "subharmonics and resounding frequencies" that a single recording keeps (source: s-tw087-music-theory-a-modern-approach; see instrument-design).

How IT allocates channels (from the manual and format doc)#

• Cut stops the old note "like in all other trackers"; continue lets it play on (a snare keeps ringing under the kick placed on the very next row); note off releases it (sustain loops, envelope sustain); note fade fades it with the instrument's fadeout. S70/S71/S72 apply cut/off/fade to all notes the channel left in the background.
• Duplicate checks: DCT (off / note / sample / instrument) with DCA (cut / off / fade) stop a repeated note from piling up — the manual's guitar example: NNA continue, DCT sample, DCA fade, one sample per string, so replaying a string fades its previous note like a finger landing on it.
• Allocation: when a channel already plays, its note is flagged background and its NNA fires; the new note takes the first free virtual channel, else the quietest background channel, else it is dropped (IT 2.03+ chooses more cleverly). Background channels die when the sample ends, the envelope ends at 0, the fadeout is silent, or their volume is 0 — so always give fading notes a real fadeout; NNA fade with fadeout 0 or continue on looped samples "can easily hang a slow computer".
• Pulse: "I sincerely hope that these options do not cause the death of brilliant 4 channel music … There is truly an art in making a decent sound in as few channels as possible!"

(sources: s-it-manual, s-ittech)

Other trackers#

XM has no NNAs — the FT2 manual defines an instrument as envelopes, auto-vibrato, samples, key split and MIDI, nothing more, and the Schism FAQ's "Tell the Milky Tracker guys to add NNAs ;)" makes the same point about FT2-style trackers (sources: s-ft2-manual, s-schism-tracker-wiki). openmpt implements IT's in full — Note Cut (default), Continue ("mostly useful with short one-shot samples such as percussion"; looped samples continue "indefinitely until you trigger one of the 'Past Note' effects S70, S71 or S72"), Note Off, Note Fade (equals Continue when Fade Out is 0) — plus Duplicate Note Checks by note, sample, instrument or plugin with their own action, and calls NNAs "a great way to save pattern channels that would otherwise be used just fading out playing notes" (source: s-openmpt-manual-instruments). Chip trackers have nothing comparable — the chip has no spare voices, which is why channel-interleaving exists.

Related#

instrument-envelopes · channel-interleaving · impulse-tracker · gravis-ultrasound

Sources#

s-tw081-it-tip-of-the-week · s-tw075-it-percussion-tips · s-ft2-manual · s-schism-tracker-wiki · s-openmpt-manual-instruments · s-tw098-impulse-tracker-midi · s-it-manual · s-ittech · s-tw087-music-theory-a-modern-approach · s-tw062-interview-vegas