DouKaku?

package require snack

set C     262
set dur   4000
set beat  5000
set amp   30000
set score cdefedcrefgagfercrcrcrcrcdefedcr

set freq $C
foreach note {c _ d _ e f _ g _ a _ b} {
  set freq [expr {$freq * pow(2, 1. / 12.)}]
  set osc  [snack::filter generator $freq $amp 0.0 sine $dur]
  snack::sound $note
  $note filter $osc
  $note length $beat
}
snack::sound r; r length $beat

snack::sound snd
foreach note [split $score {}] {
  snd concatenate $note
}
snd play -blocking yes
# snd write kaeru.wav -fileformat WAV