If your NeoTrellis M4 is powered by your computer USB, first thing to try is decoupling any ground loops by using headphones or a powered speaker running from a battery pack.

If it persists, there's a chance you're hearing serial data being transferred over the USB port, which can be noisy. This is the trade off of going with plain DAC output as opposed to I2S. It is meant to be a simple audio playback toy, not audiophile quality :)

You may also want to try powering the NeoTrellis M4 over a USB battery pack instead of your computer.

The 16-step sequencer 'sampler' demo where you can record audio onto the board depends on audio being stored in the flash memory, which is also where circuitpython stores files, so if you play one of the 'prerecorded' audio clips it will play files on the file system!

You can solve this by loading CircuitPython back onto the board, then removing all the WAV files.

Some computers, especially Mac's, will write a small amount of data after a few seconds, this causes CircuitPython to (correctly) reboot, and you'll get the audio re-start after a few seconds.

Correct, these are Arduino programs. Once you're done with these examples, re-visit the CircuitPython for NeoTrellis M4 installation page and re-install CircuitPython

You're hearing the output capacitors discharge after not playing audio for a while. This normal, not harmful, and occurs with some headphones/speakers

It's possible to accidentally "press" a column of four buttons even when you intend to only press one. This can happen when you press a button at an angle other than straight down on top of the button pad. The elastomer conductive part touches the NeoPixel ground pin against the column which makes the chip think the whole row/column is pressed. It only happens on some buttons and some angles, and is not common

It's not harmful, and there's a few ways to avoid it:

• Press straight down on buttons not at an angle
• Cut a thicker top panel from wood/plastic/3D printing so that the buttons cannot be pressed at an angle
• Read buttons via the https://github.com/adafruit/Adafruit_NeoTrellisM4 library which will do a software filtering to remove the duplicate button presses

If many of the NeoPixels are at close to full brightness, you will draw too much power from the USB port on your computer. Try lowering the brightness. If you are using the adafruit_trellism4 library, you can use the .brightness setter to lower the brightness (1.0 is max; try 0.2 or 0.3).