First let me check the working directory, then I'll create index.html that uses tone.min.js.

Build the app. A piano keyboard of 2 octaves or so, ADSR via Tone.PolySynth or Tone.Synth (which has built-in ADSR). For control over ADSR parameters, using Tone.Synth directly would be better. Keyboard mapping: the A S D F G H J K row = white keys, W E T Y U = black keys. Mouse control with a mousedown/drag (glissando) feature. Visual key press feedback.

Going to use 2 octaves: C4–B5 (15 white keys). White keys: C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 G5 A5 B5. Black keys: C#4 D#4 F#4 G#4 A#4 C#5 D#5 F#5 G#5 A#5.

Keyboard mapping (standard):
- Bottom row: C4=Z? Better to use the top-row style. Common mapping:
  White keys: A S D F G H J K L ; ' → C4 D4 E4 F4 G4 A4 B4 C5 D5
  Black keys: W E T Y U O P → C#4 D#4 F#4 G#4 A#4 C#5 D#5
That gives 2 octaves from C4 to C5 plus... hmm. Let's make it 2 octaves from C4 to B5:
  White keys: C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 G5 A5 B5 = 15 keys
  Mapping: C4=Z D4=X E4=C F4=V G4=B A4=N B4=M C5=Q D5=W E5=E F5=R G5=T A5=Y B5=U
  Black keys: C#4=S D#4=D F#4=G G#4=H A#4=J C#5=2 D#5=3 F#5=5 G#5=6 A#5=7

This is the classic 2-octave layout. Good.

ADSR: use an oscillator + Tone.AmplitudeEnvelope per note? The simplest is: a Tone.Synth per note? Better: a shared PolySynth with an ADSR envelope object; add sliders for the ADSR parameters, volume, and waveform. That would be a nice finishing touch. Use Tone.PolySynth(Tone.Synth, {oscillator, envelope:{...}, volume}). Update the envelope values live via PolySynth.voice — PolySynth exposes .voice. Set .voice.envelope.attack = x, etc.

Mouse: pointerdown on a key → triggerAttack; pointerenter while mouse button is pressed → glissando; pointerup/leave → release. Use a global pointerup.

Visuals: CSS keys, pressed-state class, active notes.

Start Tone on a user gesture: await Tone.start() on the first interaction.

Write index.html.

There's a small bug: the window pointerup handler references `mouseHeldNotes` before its declaration — but it's declared with `var` later, and gets hoisted as undefined until assigned... Actually, `var mouseHeldNotes = {};` is declared later in the same IIFE scope — it's hoisted, and the pointerup handler runs after script execution is complete, so mouseHeldNotes will be initialized. No problem. Also, there's a redundant, meaningless line `NOTES.forEach(function (n) { if (n.b) return; });` — harmless but I'll remove it.

Also, I should check whether fmsine works with PolySynth's oscillator type — does Tone support "fmsine" as an oscillator type in v14+? Tone.Synth's oscillator accepts types including "fmsine", "fmsquare", etc., via the Tone.Oscillator type list. Yeah, in Tone.js 14 the oscillator type includes fmsine. No problem, but the default fm ratio is 1, so it might sound like the base sound. OK.

I'll remove the meaningless line, then verify the HTML with a node check (can't run the browser, but a simple syntax check of the inline scripts).

Verify whether the inline JS parses correctly: extract the script and run `node --check`. Note that the script uses browser globals, but `--check` only performs parsing.

Complete. Might also verify the Tone version. It's fine. Wrapping up.