1. The VI Concerti Armonici by Unico Wilhelm van Wassenaer were probably written for a chamber music setting with one instrument per part. We do not know which basso continuo instrumentation was intended or preferred by the composer. The instrumentation experiment with just harpsichord for the basso continuo line supports the idea that in the collegium musicum, only a harpsichord could have been used. The informal setting of the collegium musicum gatherings, which probably took place in large rooms, did not need a lot of projection compared to a ball room or concert hall.
2. It is possible that the double bass was used to double the bass line in this music. There were instruments and players around at the time in the Netherlands. It is sure that double basses were used in instrumental music similar to the VI Concerti Armonici, such as the concertos by Arcangelo Corelli, Guiseppe Valentini and Georg Muffat. From paintings from the Netherlands, there is evidence that the double bass was not just played when all other parts were doubled too, but that it was used in relatively small settings such as the collegium musicum environment of Van Wassenaer.
3. If the double bass was used, it is reasonable that it was used in a different way than in the more usual 'concerto grosso' style. The music is written differently and gives less opportunity to drop out or join in on logical moments, so the double bass would probably have been playing the whole piece through.
4. It is also possible that a theorbo was used, as it was still around and used as a continuo instrument in the 1730's. The experiments show that the use of the theorbo turns out to be very effective when the bass part is doubled by a double bass in the 16 foot register.
5. It it also very likely that in instead a double bass, a large bass instrument in 8 foot register was used for the continuo. There is evidence that supports the idea in the Netherlands, a basso continuo line was doubled with an instrument larger than the violoncello used for the obligato line.Therefore, doubling the bass line with an 8 foot violone or another string instrument of similar size seems more logical than adding a violoncello to the basso continuo. The experiments show that also from an artistic point of view, this option is a likely one.
6. The choice of basso continuo instruments has a lot of effect on the general ensemble sound. Therefore, a performance in a concert hall could demand a different instrumentation than a large room in order to project well into the hall.