aplay: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/aplay - from package: alsa-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/aplay - from package: alsa-utils

You may install the required package with command apt-get install {package}

Error in other languages:
aplay: bevel nie gevind nie
aplay: comandă negăsită
aplay: comando não encontrado
aplay: commande introuvable
aplay: command not found
aplay: käsku ei ole
aplay: không tìm thấy lệnh
aplay: komanda nerasta
aplay: Kommando nicht gefunden.
aplay: kommandot finns inte
aplay: komut yok
aplay: nie znaleziono polecenia
aplay: níor aimsíodh an t-ordú
aplay: no se encontró la orden
aplay: no s'ha trobat l'ordre
aplay: opdracht niet gevonden
aplay: parancs nem található
aplay: perintah tidak ditemukan
aplay: príkaz nenájdený
aplay: příkaz nenalezen
aplay: команда не найдена
aplay: командата не е открита
aplay: 命令找不到
aplay: コマンドが見つかりません