But the security guard was pretty upset by the sound this organist was creating and said the sounds reminded her of a situation when an organist plays clusters with his elbows at random.
I should add that this guard loves organ music in general, she loves my rehearsals and says she could listen to them all day (and night) long.
And yesterday I received a message from my friend Marcel from Canada who in his own words also recounted similar stories with mixtures (people leaving the recital or going to the part of the church where high-pitched screaming mixtures would not be a problem).
Some people hate sound of the mixtures. Let's consider why.
Let's start with raising a question such as this: if I was playing a similar piece, how this security guard would have reacted? She loves how I play so she naturally might be predisposed to like even sounds and pieces that normally she would refuse to listen to (her story would be something like this "Vidas plays this piece so this must be good music and a great sound. If I don't like it, it's my fault so I should at least tolerate it").
Many of today's modern organs have mixtures which are too harsh for the environment they are in. We must remember that when we register a piece. In this case it might be that even some organists rightly hate such mixtures.
That's why it's better in some situations (if the range permits) to play some pieces one octave lower (like Toccata by Widor) to reduce the effect or to omit mixtures but add a few of high-pitched stops and mutations.
Then there is a question about people with hearing aid. I heard an opinion from Prof. Quentin Faulkner at the time I was studying in US, which resonated with me that harsh mixture sounds clash and interfere with hearing aid. In other words, because hearing aid lets a person hear sounds louder, these mixtures simply become unbearable.
I think we as organists should take great responsibility of what we play and how we play and register the music we play in public. In some extreme cases people who hate mixtures might start to hate organ and its music in general.
When we choose a repertoire for recitals, we must think about the instrument, about the people and about the occasion and aim to have balance between loud and soft, joyful and sad, high and low sounds, fast and slow pieces. Maybe then a little of harsh sound of mixtures interspersed with flutes, strings, principals and reeds will be interesting enough and not become a burden to some of our listeners (and ourselves).
PS. Avoid practicing on your own with harsh mixtures all the time (even when the piece demands it). They may indeed be harmful to our ears. One or two flutes is usually sufficient.
Remember this - practice is not rehearsal and certainly not the same as performance.