The player on Realbook.site sounds the way it does thanks to recordings and software that other people chose to share. Thank you.

Sounds

• Piano — Salamander Grand Piano V3 by Alexander Holm, CC BY 3.0. Two of the sixteen velocity layers, mixed to mono, shortened and compressed for the web.
• Double bass — VSCO 2 Community Edition (Solo Contrabass, pizzicato) by Versilian Studios, CC0 1.0. Mixed to mono, shortened and compressed for the web.
• Drums — Virtuosity Drums by Versilian Studios, played by Austin McMahon, CC0 1.0. Mixed to mono, shortened and compressed for the web.
• Brushes and all other instruments — FluidR3_GM soundfont, via midi-js-soundfonts by Frank Wen; web edition by Benjamin Gleitzman, MIT License. Copyright (c) 2000-2002 Frank Wen. Brush samples are extracted and stored on the site; the other instruments stream from the web edition, with levels matched per instrument.

Software

• Music engraving — Verovio by RISM Digital Center and contributors, LGPL 3.0.
• Audio engine — Tone.js by Yotam Mann and contributors, MIT License.
• Soundfont player — soundfont-player by danigb, MIT License.