Song JSON v1 スキーマ
{ v:1, title, bpm, rpb:4, rows:32, swing, echo,
meta:{root:57, scale:'minor'},
instruments:[{name, wave:'pulse'|'tri'|'saw'|'noise',
duty:.125|.25|.5|.75, vol, a,d,s,r, vib, vibRate,
vibDelay, slide, arp:'047', noiseMode:'long'|'short'}],
channels:[{name, inst}], // 4ch
patterns:[{name, ch:[[cell|null × rows] × 4]}],
order:[0,1,0,2] }
cell = { n:MIDI(Noise:0-15), l:行数, v:1-15,
i?:音色上書き, fx?:{arp:'037', slide:12} }