ossxmix: 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 Debian possible default full paths are:

/usr/bin/ossxmix - from package: oss4-gtk

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

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