Using PlatformIO

Since the application uses a lot of PROGMEM, you need to set the partition scheme to "Huge APP" is you use an ESP32. The following platformio.ini should work:

[platformio]
description = Espeak-NG Example
default_envs = esp32dev

[env:esp32dev]
platform = https://github.com/platformio/platform-espressif32.git
board = esp32dev
framework = arduino
lib_deps =
    https://github.com/pschatzmann/arduino-audio-tools
    https://github.com/pschatzmann/arduino-espeak-ng
    https://github.com/pschatzmann/arduino-posix-fs
build_flags = -DCORE_DEBUG_LEVEL=2 -Wno-unused-variable -Wno-unused-but-set-variable -Wno-unused-function -Wno-format-extra-args 
monitor_speed = 115200
monitor_filters = esp32_exception_decoder
board_build.partitions = huge_app.csv