Harmonic Analysis Tool (HAT) App


An important part of this project involved creating an application program to analyze, visualize, and compare tone quality. Like all software development projects, it is never really done. At this time the code is primarily implemented to support analysis of notes that have been recorded by other means. The tool is not ready for external distribution at this time. One of the long term objectives for this project is to build a tool with an intuitive user interface that can run on a mobile device like a tablet. A musician would be able to use HAT in a practice environment.

HAT RTA screenshots

The rest of this page contains screenshots along with information about what the screens are showing. If you prefer, the video page has a short 3 minute demo of some of the features.

Harmonic spectrum bar chart

There are many real-time analyzers (RTA's) that will show the spectrum (harmonics). Most of them are truly real-time, meaning they show the information while a note is being played. Once the note terminates, the display ends. HAT will show a real-time display, and when the note ends it will display the averages of each harmonic.

Straight Tone: B4
RTA bar: B4

The screenshot is showing a HAT display after the note B4 was played. The left half of the screen is showing a bar chart. The solid color bars indicate the average for each harmonic. The top of the hollow grey box on the upper part of each bar is showing the maximum, and the bottom of the grey box is the minimum.

The lower right part of the screen shows the amplitude (loudness) of the note with time as the horizontal axis. The light grey vertical lines are spaced one second apart.

The plot above the amplitude is the pitch with time as the horizontal axis. The note's average pitch is shown as a horizonal line, and vertical bars above (or below) the line indicate that the pitch at the interval is sharp (or flat). The horizontal lines above and below the pitch indicate a quarter-tone difference from the average pitch.

HAT line chart screenshots

For a more detailed view of the harmonics, line charts are available. Rather than a simple average, it is possible to view the harmonics over time. This is particularly useful when looking at how the spectrum changes during a note. Even when flutists play without vibrato, there is some variation in the timbre. Also, when vibrato is introduced the harmonics, amplitude, and pitch all fluctuate.

In the line chart display, the fundamental is white. The other harmonics use the color coding mentioned in the background webpage (yellow represents harmonics 2 and 4 which are octaves above the fundamental, green represents harmonics 3 and 6 which are fifths, etc).

One additional observation is that the harmonic mix (or signature) is different for various pitches.

Harmonic spectrum line chart: B4

Straight Tone: B4 Vibrato: B4
RTA line: B4 RTA line: vib B4

Harmonic spectrum line chart: D4

Straight Tone: D4 Vibrato: D4
RTA line: D4 RTA line: vib D4

D4 Different Flutists

Flutist 1 Straight Tone: D4 Flutist 2 Straight Tone: D4
RTA line: D4 RTA line: D4

B4 Teacher vs. Student

Teacher: B4 Student: B4
RTA line: teacher B4 RTA line: student B4