Although the bassoon is not well known as a concerto instrument, it does have an interesting timbre, but can be agile despite is pitch and Williams' concerto, The Five Sacred Trees was fairly successful. Unfortunately, no matter how forcefully the arguments are put, thinking of the tuba as agile is fairly difficult and despite his best efforts, I still find myself unconvinced of its merits. The concerto is written as a single movement, although it is fairly obviously divided into a lyrical opening movement (faintly reminiscent of The Reivers), a fairly ponderous middle cadenza section and a sprightly final movement. The middle section is where the timbre limitations of the tuba are most evident, there simply isn't much scope for interesting dynamics. This results in the momentum dying and the interesting waning.
One thing I often ask myself when listening to a concerto is, would the piece be any different (for better or worse) without the solo instrument? Particularly during the otherwise enjoyable first and last movements, the tuba almost feels in the way, which is obviously not the desired response in the listener. It feels like an interesting experiment, but in practise we're just waiting for the orchestral flourishes to return. I wonder if transcribing it for double bass (or even bassoon) might work, at least the bass has the flexibility of a string instrument, with a far wider range in both dynamics and pitch. It should be noted that I have seen the concerto performed in concert conducted by the composer and the whole thing was played considerably faster, which did help keep it going. Unfortunately the performance here is a little lackluster and even the soloist seems a little lethargic, although that may be a side effect of the instrument.
The harp seems to be gaining in popularity as a concerto instrument. As I've mentioned elsewhere, as it quite delicate and easily obscured, the orchestra must be handled carefully in order that it can have correct prominence. Germaine Tailleferre has taken heed of this and uses the trick of the harp playing either alone or against the smallest of forces, apart from on a few occasions when it seems to retake the instrument's usual position in the orchestra playing gentle glissandos in the background. The opening movement has a quasi baroque feeling to it, while the predictably gentle Lento is fairly impressionistic. The final movement is a little more sprightly, although the harp seems less of an important feature than previously. Pleasant, but not hugely interesting musically and certainly not as dynamic as Kevin Kaska's Harp Concerto.
Michael Kamen wrote a very enjoyable saxophone concerto, although in a slightly more contemporary idiom. Here, Henri Tomasi places it into a more traditional setting, in fact at times, one might think it was a clarinet - the instruments are of course related, but the sax has a much more gutsy sound. Even so, Tomasi's striking and bold orchestral gestures do seem a little bit grand, especially in the opening where the sax plays in a slightly submissive role, rarely striking out to match the rest of the orchestra. Percussion composition can often fall somewhat flat, especially for untuned instruments (i.e. drums, cymbals, triangle and so on), but for there are some quite fun opportunities with tuned and the xylophone has often featured prominently. There is almost no range in timbre and little in dynamics, so it's essentially an exercise in technical expertise and Mayuzumi's composition doesn't disappoint, with plenty of rushing about and no small number of witty moments of the soloist attempting to copy the orchestra.
As mentioned with regard to the Tuba Concerto, the playing of the orchestra does seem ever so slightly insipid. It certainly lacks the zip and dynamism one hopes for. The pretty unimpressive recording - it's not bad as such, just a little bland - doesn't help either. Some interesting ideas, but I suppose there are reasons composers have always come back to the violin for their concerti, it has the greatest range of emotion of any instrument and can be played in so many different ways, others just seem too limited in comparison. For readers of this site the album is primarily of interest to Williams fans, but despite some fun orchestral passages, the solo instrument seems redundant in its own concerto. The other compositions are of interest, but rather unlikely to be recognised as great works.
Rating ~ 
Harp Concerto (Germaine Tailleferre)
Total Time ~ 68:33