Following 9000 Series, I also found a sound of Tokyu first 5000 Series, which had run some Tokyu lines between 1954 and 1986 and was affectionately nicknamed "green frog" after its roundish body and colour. Thuogh it reminds me of nothing, some railfans born in 1950s or 1960s may have memories of it.
The characteristic point of the sound is the silence which cardan drive whose motor was laid out to be perpendicular to axle made. Perpendicular cardan drive improved some demerits of nose-suspended (Sprague) drive such as motors' weight pressing wheel and axle and damaging the railway, which cause big noise and vibration.
After the retirement in 1986, some carriages moved to some rural railways, such as Fukushima Kotsu, Ueda Electric Railway, Nagano Electric Railway, Alpico Kotsu, Gakunan Railway, and Kumamoto Electric Railway. However, in 2015, none of them but the one on Kumamoto Electric Railway were replaced by another carriages, and the last remaining is retiring by March, 2016..
Some carriages are now preserved at several places. In front of Shibuya Station, the first-made front carriage, 5001, whose body length was shortened, stands and some photographs of the scenery in Shibuya. In Nagano Prefecture, four front carriages are displayed at two different places; two of them are in Niimura train shed on Alpico Kotsu Kamikochi Line in its original green colour, and the others are in the parking of Train Gallary NAGANO in Nagano Electric Railway's red and light yellow colour.
Though first 5000 Series had retired from Tokyu when I was born, I wish the carriage keep being beloved and saying its episodes as a historic carriage on a technical aspect repeatedly by many railfans who don't know its service on Tokyu.