This shield can read audio from an SD card and play back multiple types of sound files, including MP3, AAC, WAV, and more. You can digitally adjust the sound quality and play it out through the included stereo amp. Sparkfun also has a version of an MP3 shield here, but it doesn't read as many types of files.
Like the previous shield, this shield allows you to read and control audio files, this time specifically MIDI ones. It also comes with two potentiometers and two MIDI connectors so you can control synthesizers, sequencers, and other musical devices directly from your Arduino. With a MIDI shield and an MP3 shield, you can read pretty much all audio files out there!
The chip on this shield contains a musical instrument database that allows you to play sounds from a piano to a trombone. You can connect to the headphone jack to hear your created symphony. The sound files use a MIDI codec to create great-sounding instruments for your next musical project.
This shield is geared towards producing high-quality sound output. You can play files from a MicroSD card to connected headphones or speakers. The potentiometer allows you to control volume from the Arduino. This kit comes with the shield, an SD card, and a speaker so you can get started right away.
The Voicebox shield uses the SpeakJet chip to synthesize a robotic voice. You can read out commands from your program to add a voice to your robot, personalize your project, or just freak people out. If you want to know what the voice sounds like, try the "say" command on Mac terminal.
If you want to be able to talk back to your robot, you'll need this shield. It uses EasyVR to download and parse speaker input for recognizable vocabulary to act on. You can use this in conjunction with the voicebox shield to have a full conversation with your project if you'd like.