I have developed a ministry of humming.
Humming is not the same as singing. It's normally quieter for a start.
I found myself doing it quite a lot this summer, especially in settings where singing in tongues was taking place, though I'm not aware of any biblical references to humming...(this was generally not during Anglican morning worship by the way; more in big Christian camping venues or tiny Welsh revivalist chapels).
Singing in tongues is an interesting phenomenon. For a more scholarly article on it see: http://www.pneumafoundation.org/resources/articles/rwgraves010.pdf
St Paul mentions it in 1 Corinthians 12 ('I will sing praise with the spirit but I will sing praise with the mind also') - it was clearly a feature in the church of the years immediately after Christ.
In practice it appears to function well within the context of extended, contemporary musical worship, as Peter Ward describes in Selling Worship: 'In charismatic worship the songs function (...) as the means to encounter with God' (p. 199). In other words, it comes with its own theology of the mediation of God's grace, which is quite different from (or perhaps not?) sacramental theology...
If you have a competent and more importantly, sensitive band, they can lead seamlessly from a known song into a more improvised time where people are encouraged to sing extempore, sometimes singing in their mother tongue, words or phrases that the Spirit inspires, often short phrases from the bible, or else genuinely singing in an unknown tongue, or 'glossolalia'. The effect can be, quite simply, beautiful.
But musically it all needs a bit of glue.
It needs to hang together harmonically. Sometimes the band will play a 'sostenuto' chord over which singers find harmonies; sometimes they'll play a more complex series of chords.
People need encouraging to sing out in improvisation; tongues is the jazz of church music. Humming is a useful place to start and harmonically flexible. A chord is made up of three notes; usually the first, third and fifth. If you can hear the first and fifth, you can hum a third to hold it (glue it) together. If you can only hear a third and a first, you can hum a fifth. Its all about listening. When the chord has been established you can let the words come.
In fact it hadn't occurred to me with such force before that in worship we're required to endlessly listen. Obviously to God, but also to each other. If you are fortunate enough to be somewhere where there's ample leisure to spend extended time in God's presence, humming can glue the combined sound together, leaving your mind free to receive whatever God wants to say to you. I had all sorts of ideas and pictures while humming in venues through the summer.
Humming is invisible. Undemonstrative glue. Broken things often needs glueing together.
Humming in harmony, adding to the praises of God's people, being a perfect picture of the symphony of the body, each person giving his or her own best, without being pushy. Or simply listening and receiving. One of the 'new (spontaneous) songs' we heard at New Wine this summer was 'Just simply be in my love.'
It has always been noticeable how much more frequent are people's stories of physical or emotional healing during this kind of worship. It's not even 'singing in the Spirit' - more 'singing the Spirit'.
Humming is background; it doesn't put itself up front...you can't quite pin down where it's coming from but without it things might start to fall apart a bit.
It's what a parish priest aspires to: presence as glue - effective but often unnoticed - a community often unable to quantify quite what that presence means but poorer without it.
I'm not sure what St Paul would have made of it, but here's to humming in the Spirit.
(This song (imagine no drums and just the chords) seems to lead well into improvisation: be patient, give it time; be open.