nx_song_grade.nx

nx_song_grade.nx -- INSTRUMENT-LEARN-GAME (Rocksmith-class) rung LG-2: the score-follower / grader. Given a SONG (a sequence of target notes with timings) and the PLAYER's recorded audio, it grades every note the player attempted -- HIT (right note), WRONG (a note, but the wrong one), or MISS (nothing played) -- and returns an overall score. This is the core teaching loop of a learn-game: play along, get graded, see what you missed. Works for ANY monophonic instrument (guitar single notes, bass, violin, voice, wind) -- it stands on nx_pitch (F0) -> nx_note (F0 -> MIDI). Polyphony (chords) is a later rung (LG-3, needs the nx_fft spectral path). SONG layout (caller-owned *i64, 3 words per note): score[i*3+0] = target MIDI note score[i*3+1] = note start sample score[i*3+2] = note duration in samples nx_song_grade(score, n_notes, player_pcm, fs, tbl, verdicts) -> score_permille verdicts[i] = SG_HIT / SG_WRONG / SG_MISS returns hits * 1000 / n_notes (per-mille accuracy) tbl = a 128-entry note table from nx_note_table. license_tier: ORIGINAL module: nishi-core.audio.song_grade depends: nishi-core.audio.note, nishi-core.audio.pitch capability: AUDIO_LEARN_GAME