Day 17: MIDI & the Piano Roll
Tuesday, April 14th, 2026
Warmup
Login to Clever and watch the Edpuzzle video about MIDI. In the video Colin explains what MIDI is. The Musical Instrument Digital Interface (MIDI) is a way for electronic instruments and computers to communicate. It allows you to control virtual instruments, like the drum kit in GarageBand, using a MIDI controller or by programming patterns in the piano roll.
In the video he uses microcontrollers and MIDI to make a drum machine.
As you watch, jot a quick answer to these on the back of your drum worksheet packet:
- What do the letters M-I-D-I stand for?
- Is MIDI audio (actual sound) or instructions (telling an instrument what to play)?
- Name one thing MIDI lets you do that a plain audio recording cannot.
Work Session
What Is the Piano Roll?
Before MIDI, before computers, there were player pianos — real acoustic pianos that could play themselves. Instead of a person pressing the keys, the piano read a long sheet of paper called a piano roll. The paper had holes punched in it, and as the roll scrolled past a reader bar, each hole told the piano which key to press and how long to hold it. Wider holes meant longer notes. Holes further to the left or right meant lower or higher pitches.
That idea never went away. When digital audio workstations like GarageBand were built, engineers borrowed the same visual language: time flows left to right, and pitch is stacked top to bottom. A note is just a rectangle — the longer the rectangle, the longer the note holds. Instead of punching holes in paper, you click and drag to place notes on a grid.
For drums, each horizontal row in the piano roll is a different drum sound (kick, snare, hi-hat, etc.) instead of a different pitch. That’s what the MIDI drum mapping table is for — it tells you which row plays which drum.
Understanding MIDI Drum Mappings
In GarageBand’s piano roll, each drum sound is triggered by a specific MIDI note number. The note you click determines which drum sound plays.
Refer to the MIDI Drum Mappings page for the complete guide to which notes control which sounds. You’ll find a quick reference table of the most commonly used drums (kick, snare, hi-hat, toms, cymbals) as well as the complete General MIDI drum map.
The drum notation key shows how these sounds are notated on the staff. Drum Notation Key.
Programming Your First Drum Beat
Grab your printed Drum Worksheet Packet from Mr. Willingham. The packet shows each beat of the measure broken into grid squares — exactly like the piano roll in GarageBand.
Create a new Drummer/Drum Kit track
Open GarageBand and add a Software Instrument track with a drum kit patch. Open the piano roll (double-click the region or press E).
Find your drum notes
Using the MIDI Drum Mappings table, locate these three rows on the piano roll:
- C1 (36) — Kick
- D1 (38) — Snare
- F#1 (42) — Closed Hi-Hat
Program “Rock Steady”
Follow the Rock Steady pattern on your printed packet. Click once in each grid square that has an X. Work one drum at a time — hi-hat first, then kick, then snare.
Loop it and listen
Press the spacebar to play. Does it sound like a beat? If something feels off, check the grid against your packet square-by-square.
If you finish early, try programming the Add Toms pattern, which adds toms and cymbals to the mix. Use the MIDI mappings page to find the right notes for each tom and cymbal.
Closing
Return Your Packet
The Drum Worksheet Packet is a class set. Leave it in class.
Exit Ticket
Before you leave, be ready to answer:
- What MIDI note triggers the kick? The snare? The closed hi-hat?
- Why is MIDI more flexible than recording a drum loop as audio? (Hint: think about changing the tempo or swapping the drum kit.)
Standards
- MSMTC8.CR.1 — Generate musical ideas for various purposes and contexts (programming rhythmic ideas using MIDI note numbers in the piano roll).
- MSMTC8.CR.2 — Select and develop musical ideas for defined purposes and contexts (selecting drum sounds and arranging them into a complete beat pattern).