Coste’s working relationship with Lacote was evident by 1835. Besides building guitars, Lacote was dealing in other instruments and presumably also selling strings and other accessories from his workshop in Paris. This included music, and his name appeared on the title page of Coste’s first published work, Opus 5, Souvenirs de Flandres.
Lacote’s marketing of Coste’s publication would imply that their partnership to promote the instrument was well underway. Coste not only played a key role in its development but would go on to compose extensively for the guitar he would christen the Heptachorde. He would later recount his collaboration with Lacote in the appendix to his 1851 method book:
“Some years ago, in the workshops of M. Lacote, luthier in Paris, I made a guitar whose construction was researched in such a way as to provide a greater volume – and above all a more beautiful quality – of sound. This attempt was successful, in this sense, that I obtained almost double the volume of sound of ordinary guitars, and the quality was incomparably more beautiful. The addition of a seventh string completed the instrument’s design . . . I gave to this new instrument the name of Heptacorde.”
In his Method, Coste provides a clear description and justification for the seventh string:
“The seventh string (usually D, but sometimes C) is placed away from the others and does not alter the performance and without it being plucked, it gives more power to the instrument. Without it some composers such as Giuliani and Legnani employ, for example, a first inversion D Major chord (i.e. F # in the bass), made even more deplorable by doubling the 3rd, but if they had the means they would not have hesitated to do. The D minor chord is very awkward on the ordinary guitar, and never answers well to the proceeding chord.”
He goes on to explain the inspiration for adding a seventh string and its advantages:
“My illustrious colleague SOR was so struck by the lack of a low tonic note in the key of D that he seldom wrote in this key without lowering the sixth string by a tone. But this alteration in the tuning has the inconvenience of depriving the composer of ease of modulation, and thus restricts the harmony within a narrow circle.”
It is probable that Coste customized his Lacote Heptachorde guitars (as evidenced in photographs) by adding a finger rest and later, a tailpiece and pass-through bridge.
The 1840 Lacote Heptachorde in the Austin-Marie Collection is understated, with back and sides of flamed maple and a spruce top. The headstock is faced with the Lacote a Paris logo and is appointed with the signature Lacote enclosed tuners.