sidplayfp: 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/sidplayfp - from package: sidplayfp

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

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