G01, also known as the Tyrolean Music Station, was operated by the French external intelligence agency SDECE^[3][4][5] - Service de Documentation Extérieure et de Contre-Espionnage (External Documentation and Counter-Espionage Service), the predecessor of the DGSE. Transmissions ceased in 1975, in the few following days after the French anti-establishment magazine Interférences published the information that the station was operated by the SDECE from the area of Chartres, in France^[3]. It was quite a unique station: rather than simply broadcasting groups of numbers, it also occasionally sent messages as coded sentences - similarly to the better-known example of Radio Londres's "personal messages" to the French Resistance during WWII.

G01 transmitted every Saturday and Sunday at 11:30 UTC, simultaneously on 6425 kHz and a second frequency around 6660 kHz (several sources mention 6640, 6650, 6660, 6665 or again 6675 kHz). G01 also operated another less known schedule, possibly on Monday and Friday evenings at 18:30 UTC on lower frequencies. As its name indicates, it made extensive use of Tyrolean music and yodeling as introduction, however in an uncommon way: transmissions happened as follows.

• At 11:30 UTC, several Tyrolean songs were played, until about 11:40 UTC.
• The carrier then stayed up but remained unmodulated, until 11:55 UTC.
• At 11:55 UTC, the first few notes of the chorus of the communist anthem The Internationale, rendered on a music box, were played in a loop, until 11:59 UTC; then a speeded-up version of this was played for one more minute, until 12:00 UTC.
• At 12:00 UTC, several German names were announced - appearing as codenames for message recipients. Then each recipient was called again and their message given as a series of 5-figure groups. Messages were announced by "Achtung", repeated, and concluded with "Ende". Messages were relatively short: a dozen groups on average.

Most of the time, the Tyrolean music introduction was made of the same three songs. Sometimes, a fourth song was also played. Sometimes, different songs from the usual ones were played instead. (These variations in songs would correspond to the G01a designator.) Sometimes, in addition to playing different songs from usual, these were interrupted by messages in the form of coded sentences - a variant known as G01b; for example: "Helmut grüßt Franz. Helmut grüßt Franz. Guten Tag! Die Größen 26 bis 32 passen mir gut. Die Sonne scheint herrlich. Unsere Henne ist dabei, ein Ei zu legen." (Helmut greets Franz. Helmut greets Franz. Hello! The sizes 26 to 32 fit me well. The sun is shining wonderfully. Our hen is about to lay an egg.) The music would be abruptly cut off at three separate intervals to switch to announcing the same series of messages each time, with the last repeat concluding with the supplementary greeting "Alles Gute! Auf Wiederhören!" (All the best! Goodbye!), before switching back to the music.

In known recordings of G01, all the pieces of Tyrolean music can be identified as successive songs from the same record of Franzl Lang, the "Yodel King" singer: apparently, the first songs of the A-side were simply played in order during regular G01 transmissions, while B-side was used instead for G01b. Additionally, the voice of the announcer in those recordings can be described as speaking German with an Alsatian accent, which may be connected to the French origin of the station.

Operations of this station were described as amateur, with frequent technical glitches such as tapes being rewound, clicks, coughing and other sounds heard on the air, among other handling mistakes.

References

1. Simon Mason's website
2. ENIGMA Newsletter #3
3. Long-lost evidence shows G01 run by French SDECE - priyom.org
4. Espionnage et radio - Interférences (Pour une Critique des Appareils d'Information et de Communication) #3 (Fall 1975), p. 9
5. Histoire politique des services secrets français : de la Seconde Guerre mondiale à nos jours - Roger Faligot, Jean Guisnel, Rémi Kauffer (2013), p. 207