Notes for Class No. 15

Introduction to Playing and Transposing Music Using Lists

https://www.youtube.com/watch?v=EKiqthx0GKw

Understanding the blocks related to lists

Editing list values

Extending the concept of intervals to “deltas” or “offsets”

as offsets from the starting note (the first note of the piece)
as offsets from the tonic note (the “key” note of the piece)
as offsets from the previous note (the one that immediately precedes it in the list)

Code for the following demonstrations

https://scratch.mit.edu/projects/54423380/#editor

Playing a list containing the MIDI values of a harmonic minor scale using a straight sequence of play note blocks

Playing that list using a loop

Transposing the scale into any key

Review: What is a delta?

Coding the list using deltas (or offsets) from the tonic (or key) note

Coding the list using deltas to each note from the preceding note

on Windows, right-click the list, or on Macs, Ctrl-click it, to bring up the import / export / hide popup menu
if you hide the list, Scratch will execute a bit faster
if the list is hidden, display it by clicking the check box next to the list name in the Data section

loops and how they can be used to play all the notes from a list
“deltas” or “offsets”
- “delta” is the Greek letter Δ
- it is typically used to denote a change from one value to another
- in the context we’ve been talking about, a delta and an offset and a change are all the same thing
different ways to play music from a list in different keys
- by adding a delta or offset to the note value read from the list
- by reprogramming the list itself to contain deltas (or intervals) rather than absolute note values
different ways to use deltas in lists
- as offsets from the starting note (the first note of the piece)
- as offsets from the tonic note (the “key” note of the piece)
- as offsets from the previous note (the one that immediately precedes it in the list)

Harry Potter Theme