It is well known that music is a great memory aid and, in our family, we’ve used Japanese music to great effect as a fun way to improve language skills. We were lucky enough to have received these Kumon nursery rhyme / folksong CDs from a cousin in Japan when our first child was born and we’ve gotten a ton of use out of them. We received three CDs with 30 songs and lyric cards each and have played them a lot with the kids over the years.
A non-obvious benefit that we received from immersing the family in this music has been a big dose of Japanese cultural reference in addition to merely reinforcing vocabulary and grammar. A few years ago, we were visiting Kyoto and dropped by こどもみらい館 for some morning activity time. When song time started up, we were ecstatic to realize that we knew all the songs and our kids could participate fully as a result! These traditional Japanese children’s songs are also used all the time in Japanese day care and it’s been beneficial for our kids (and us parents!) to be able to join in effortlessly due to an existing familiarity with this fundamental cultural element.
Of course, there are plenty of other sources of music & videos online, often with accompanying subtitles to aid in understanding for kids and non-native Japanese parents alike. Some favorites of ours have been useful for fundamentals like hiragana, days of the week and even this wild one filled with puns and Japanese counters: