After reading your Blog article here: https://www.pschatzmann.ch/home/2025/09/23/arduino-audio-tools-using-less-memory/ I tried out a small test case using PlatformIO,

Here are my results with a stripped down app: (empty setup and loop)
ini file:
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200

Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM: [= ] 6.4% (used 21032 bytes from 327680 bytes)
Flash: [== ] 17.8% (used 233241 bytes from 1310720 bytes)

After adding library reference:

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
lib_deps =
https://github.com/pschatzmann/arduino-audio-tools

and adding the include statement:

#include "AudioTools.h"
// put function declarations here:
void setup() {
// put your setup code here, to run once:
}
void loop() {
// put your main code here, to run repeatedly:
}

I gain a lot more flash usage:
RAM: [= ] 8.7% (used 28556 bytes from 327680 bytes)
Flash: [==== ] 37.7% (used 494289 bytes from 1310720 bytes)

Can anyone tell me what I am doing wrong? I am wondering if including the library directly from github could be the issue. Or am I using different hardware than you were (I am using an audiokit 2.2).