piano roll and a simple synth

What is new

• Piano roll with 60 rows (C2 to B6) and a piano key column
• Click or drag to add and remove notes, note length 1/16 to 1/2
• Synth voice with a wave choice (saw, square, triangle, sine)
• Key and scale selector, notes outside the scale are dimmed
• Play the synth with the computer keyboard (Z to M), [ and ] change octave
• Space plays and pauses